Chapter V: Introduction (4)

His first experiment, _Vegetable Staticks_, p. 100, was with a vine to which he attached a vertical pipe made of three lengths of glass-tubing jointed together. His method is worth notice. He attached the stump to the manometer with a "stiff cement made of melted Beeswax and Turpentine, and bound it over with several folds of wet bladder and pack-thread." We cannot wonder that the making of water-tight connexions was a great difficulty, and we can sympathise with his belief that he could have got a column more than 21 feet high but for the leaking of the joints on several occasions. He notes the familiar fact that the vine-stump absorbed water before it began to extrude it.

He afterwards (pp. 106-7) used a mercury gauge and registered a root-pressure of 32½ inches or 36 feet 5⅓ inches of water which he proceeds to compare with his own determination of the blood-pressure of the horse (8 feet) and of other animals. Perhaps the most interesting of his root-pressure experiments was that (p. 110) in which several manometers were attached to the branches of a bleeding vine and showed a result which convinced him that "the force is not from the root only, but must proceed from some power in the stem and branches," a conclusion which some modern workers have also arrived at. The figure on page 77 is a simplified reproduction of the plate (Fig. 19) in _Vegetable Staticks_.

_Assimilation._

Hales' belief that plants draw part of their food from the air, and again that air is the breath of life, of vegetables as well as of animals (p. 148), are based upon a series of chemical experiments performed by himself. Not being satisfied with what he knew of the relation between "air" (by which he meant gas) and the solid bodies in which he supposed gases to be fixed, he delayed the publication of _Vegetable Staticks_ for some two years, and carried out the series of observations which are mentioned in his title-page as "An attempt to analyse the air, by a great variety of chymio-statical experiments" occupying 162 pages of his book[46].

The theme of his inquiry he takes (_Vegetable Staticks_, p. 165) from "the illustrious Sir _Isaac Newton_," who believed that "Dense bodies by fermentation rarify into several sorts of Air; and this Air by fermentation, and sometimes without it, returns into dense bodies."

Hales' method consisted in heating a variety of substances, e.g. wheat-grains, pease, wood, hog's blood, fallow-deer's horn, oyster-shells, red-lead, gold, etc., and measuring the "air" given off from them. He also tried the effect of acid on iron filings, oyster-shells, etc. In the true spirit of experiment he began by strongly heating his retorts (one of which was a musket barrel) to make sure that no air arose from them. It is not evident to me why he continued at this subject so long. He had no means of distinguishing one gas from another, and almost the only quality noted is a want of permanence, e.g. when the CO_2 produced was dissolved by the water over which he collected it. Sir E. Thorpe[47] points out that Hales must have prepared hydrogen, carbonic acid, carbonic oxide, sulphur dioxide, marsh gas, etc. It may, I think, be said that Hales deserved the title usually given to Priestley, viz. "the father of pneumatic[48] chemistry."

Perhaps the most interesting experiment made by Hales is the heating of minium (red-lead) with the production of oxygen. It proves that he knew, as Boyle, Hooke and Mayow did before him, that a body gains weight in oxidation. Thus Hales remarks: "That the sulphurous and aereal particles of the fire are lodged in many of those bodies which it acts upon, and thereby considerably augments their weight, is very evident in Minium or Red Lead which is observed to increase in weight in undergoing the action of the fire. The acquired redness of the Minium indicating the addition of plenty of sulphur in the operation." He also speaks of the gas distilled from minium, and remarks "It was doubtless this quantity of air in the minium which burst the hermetically sealed glasses of the excellent Mr _Boyle_, when he heated the Minium contained in them by a burning glass" (p. 287).

This was the method also used by Priestley in his celebrated experiment of heating red-lead in hydrogen; whereby the metallic lead reappears and the hydrogen disappears by combining with the oxygen set free. This was expressed in the language of the day as the reconstruction of metallic lead by the addition of phlogiston (the hydrogen) to the calx of lead (minium). Thorpe points out the magnitude of the discovery that Priestley missed, and it may be said that Hales too was on the track and had he known as much as Priestley it would not have been phlogiston that kept him from becoming a Cavendish or Lavoisier. What chiefly concerns us however is the bearing of Hales' chemical work on his theories of nutrition. He concludes that "air makes a very considerable part of the substance of Vegetables," and goes on to say (p. 211) that "many of these particles of air" are "in a fixt state strongly adhering to and wrought into the substance of" plants[49]. He has some idea of the instability of complex substances and of the importance of the fact, for he says[50] that "if all the parts of matter were only endued with a strongly attracting power, [the] whole [of] nature would then become one unactive cohering lump." This may remind us of Herbert Spencer's words: "Thus the essential characteristic of living organic matter, is that it unites this large quantity of contained motion with a degree of cohesion that permits temporary fixity of arrangement," _First Principles_, § 103. With regard to the way in which plants absorb and fix the "air" which he finds in their tissues, Hales is not clear; he does not in any way distinguish between respiration and assimilation. But as I have already said he definitely asserts that plants draw "sublimed and exalted food" from the air.

As regards the action of light on plants, he suggests (p. 327) that "by freely entering the expanded surfaces of leaves and flowers" light may "contribute much to the ennobling principles of vegetation." He goes on to quote Newton (_Opticks, query 30_): "The change of bodies into light, and of light into bodies is very conformable to the course of nature, which seems delighted with transformations." It is a problem for the antiquary to determine whether or no Swift took from Newton the idea of bottling and recapturing sunshine as practised by the philosopher of Lagado. He could hardly have got it from Hales since _Gulliver's Travels_ was published in 1726, a year before _Vegetable Staticks_. Timiriazeff, in his Croonian Lecture[51], was the first to see the connexion between photosynthesis and the Lagado research. Nevertheless Hales is not quite consistent about the action of light; thus (p. 351) he speaks of the dull light in a closely planted wood as checking the perspiration of the lower branches so that "drawing little nourishment, they perish." This is doubtless one effect of bad illumination under the above-named conditions, but the check to photosynthesis is a more serious result. In his final remarks on vegetation (p. 375) Hales says in relation to greenhouses, "it is certainly of as great importance to the life of the plants to discharge that infected rancid air by the admission of fresh, as it is to defend them from the extream cold of the outward air." This idea of ventilating greenhouses he carried out in a plant house designed by him for the Dowager Princess of Wales, in which warm fresh air was admitted. The house in question was built in 1761 in the Princess's garden at Kew, which afterwards became what we now know as Kew Gardens. The site of Hales' greenhouse, which was only pulled down in 1861, is marked by a big _Wistaria_ which formerly grew on the greenhouse wall. It should be recorded that Sir W. Thiselton-Dyer[52] planned a similar arrangement independently of Hales, and found it produced a marked improvement of the well-being of the plants.

It is an illuminating fact that though Hales must have known Malpighi's theory of the function of leaves (which was broadly speaking the same as his own), he does not as far as I know refer to it. In his preface, p. ii, he regrets that Malpighi and Grew, whose anatomical knowledge he appreciated, had not "fortuned to have fallen into this _statical_[53] way of inquiry." I believe he means an inquiry of an experimental nature, and I think it was because Malpighi's theory was dependent on analogy rather than on ascertained facts, that it influenced Hales so little.

There is another part of physiology on which Hales threw light. He was the first I believe to investigate the distribution of growth in developing shoots and growing leaves by marking them and measuring the distance between the marks after an interval of time. He describes (p. 330) and figures (p. 344) with his usual thoroughness the apparatus employed: this was a comb-like object, shown in Plate IX, made by fixing five pins into a handle, ¼ inch apart from one another: the points being dipped in red-lead and oil, a young vine-shoot was marked with ten dots ¼ inch apart. In the autumn he examined his specimen and finds that the youngest internode or "joynt" had grown most, and the basal part having been "almost hardened" when he marked, had "extended very little." In this--a tentative experiment--he made the mistake of not re-measuring his plants at short intervals of time, but it was an admirable beginning and the direct ancestor of Sachs'[54] great research on the subject.

In his discussion on growth it is interesting to find the idea of turgescence supplying the motive force for extension. This conception he takes from Borelli[55].

Hales sees in the nodes of plants "plinths or abutments for the dilating pith to exert its force on" (p. 335); but he acutely foresees a modern objection[56] to the explanation of growth as regulated solely by the hydrostatic pressure in the cell. Hales says (p. 335): "but a dilating spongy substance, by equally expanding itself every way, would not produce an oblong shoot, but rather a globose one."

It is not my place to speak of Hales' work in animal physiology, nor of those researches bearing on the welfare of the human race which occupied his later years. Thus he wrote against the habit of drinking spirits, and made experiments on ventilation by which he benefited both English and French prisons, and even the House of Commons; then too he was occupied in attempts to improve the method of distilling potable water at sea, and of preserving meat and biscuit on long voyages[57].

Plate 18 from Hales's _Vegetable Staticks_

Fig. 40. Instrument devised by Hales to make prick-marks on a young shoot of Vine (Fig. 41); the distribution of stretching after growth is shown in Fig. 42. The use of a similar instrument for marking surfaces is shown in Figs. 43 and 44]

We are concerned with him simply as a vegetable physiologist and in that character his fame is imperishable. Of the book which I have been using as my text, namely, _Vegetable Staticks_, Sachs says: "It was the first comprehensive work the world had seen which was devoted to the nutrition of plants and the movement of their sap.... Hales had the art of making plants reveal themselves. By experiments carefully planned and cunningly carried out he forced them to betray the energies hidden in their apparently inactive bodies[58]." These words, spoken by a great physiologist of our day, form a fitting tribute to one who is justly described as the father of physiology.

FOOTNOTES:

[17] In 1699 Newton was made master of the Mint and appointed Whiston his Deputy in the Lucasian Professorship, an office he finally resigned in 1703 (Brewster's _Life of Newton_, 1831, p. 249).

[18] "There, if anywhere, his dear shade must linger," Trevelyan, _Life and Letters of Lord Macaulay_, 1 volume edit. 1881, p. 55.

[19] Black's discovery of CO_2, however, was published in 1754, seven years before Hales died, but Priestley's, Cavendish's and Lavoisier's work on O and H was later.

[20] 1837, III. p. 389.

[21] _Vegetable Staticks_, p. 346.

[22] Sachs, _Geschichte_, p. 502. Malpighi held similar views.

[23] _Ibid._, p. 499.

[24] Quoted by Caröe, in his paper read before the _Cambridge Archaeological Society_ on _King's Hostel_ etc., and "Printed for the Master and Fellows of Trinity Coll." in 1909.

[25] He also held the living of Farringdon in Hampshire where he occasionally resided.

[26] _Dict. Nat. Biog._

[27] With a certain idleness Pope reduces him to plain Parson Hale, for the sake of a rhyme in the _Epistle of Martha Blount_, 1. 198.

[28] The original reads "deigned not," an obvious slip.

[29] This he does by means of a network of threads ¼ inch apart. Pfeffer, _Pflanzenphysiologie_, ed. 1, 1. p. 142, recommends the method and gives Hales as his authority.

[30] _Pflanzenphysiologie_, 1865 (Fr. Trans. 1868), p. 254.

[31] He gives it as 15·8 square inches, the only instance I have come across of his use of decimals.

[32] _Arbeiten_, II. p. 182.

[33] See Sachs' _Pflanzenphys._ 1865 (Fr. Trans. 1868), p. 257, where the above correction is applied to Hales' work.

[34] _Vegetable Staticks_, p. 5.

[35] _Vegetable Staticks_, p. 14.

[36] _Vegetable Staticks_, p. 41.

[37] Janse in _Pringsheinis Jahrb._ XVIII. p. 38. The later literature is given by Dixon in _Progressus Rei Bot._ III., 1909, p. 58.

[38] Compare F. von Höhnel, _Bot. Zeitung_, 1879, p. 318.

[39] This is also shown by experiment XC, _Vegetable Staticks_, p. 123.

[40] The method by which Hales proposed to record the depth of the sea is a variant of this apparatus.

[41] _Vegetable Staticks_, p. 92.

[42] According to Sachs (_Geschichte_, p. 509) Ray employed this method.

[43] Other facts show that the "gapped" branches did not behave quite normally.

[44] He refers (p. 141) to what is in principle the same experiment (see Fig. 27) as due to Mr Brotherton, and published in the _Abridgment of the Phil. Trans._ II. p. 708.

[45] He notices that the swelling of the bark is connected with the presence of buds. The only ring of bark which had no bud showed no swelling.

[46] It appears that Mayow made similar experiments. _Dict. Nat. Biog._ s.v. Mayow.

[47] _History of Chemistry_, 1909, I. p. 69.

[48] Hales made use of a rough pneumatic trough, the invention of which is usually ascribed to Priestley (Thorpe's _History of Chemistry_, I. p. 79).

[49] He speaks here merely of the apples used in a certain experiment, but it is clear that he applies the conclusion to other plants.

[50] _Vegetable Staticks_, p. 313. It should be noted that Hales speaks of organic as well as inorganic substances.

[51] _Proc. R. Soc._ LXXII., p. 30, 1903.

[52] The above account of Hales' connexion with the Royal Gardens at Kew is from the _Kew Bulletin_, 1891, p. 289.

[53] I am indebted to Sir E. Thorpe for a definition of _statical_. "_Statical_ (Med.) noting the physical phenomena presented by organised bodies in contradiction to the organic or vital." (Worcester's _Dictionary_, 1889.)

[54] _Arbeiten_, I.

[55] Borelli, _De Motu Animalium_, Pt II. Ch. xiii. According to Sachs, _Ges. d. Botanik_, p. 582, Mariotte (1679) had suggested the same idea.

[56] Nägeli, _Stärkekorner_, p. 279

[57] See his _Philosophical Experiments_, 1739.

[58] _Geschichte d. Botanik_, p. 515 (free translation).

JOHN HILL

1716-1775

BY T. G. HILL

Narrative--chequered career--journalism--attack on the Royal
Society--literary activities--Botanical works--structure
of Timber--the sleep of Plants--Mimosa and Abrus--views on
Pollen--Hill's _Herbal_--his admiration of Linnaeus--with
qualifications--Hill's _Vegetable System_--an ambitious
work--financial losses--estimate of Hill's character.

It has recently been remarked that the number of the biographies of eminent men is inversely proportional to the known facts concerning them. Although this generalisation is probably incorrect, it is, to a certain extent, true of John Hill; for, although he finds a place in biographical dictionaries, apparently no extended account of his life has appeared. This is a little surprising since, apart from his scientific work, he occupied a prominent position in the middle of the eighteenth century.

John Hill was the second son of the Rev. Theophilous Hill, and was born either at Spalding or at Peterborough in the year 1716 or 1717. Nothing appears to be known regarding his early education; according to Hawkins[59] he did not receive an academical education, but there is no doubt that, as was usual for those who desired to practise medicine at that and at much later times, he served his apprenticeship to an apothecary, it is said, at Westminster; also he attended the lectures on Botany given under the auspices of the Apothecaries' Company at the Chelsea Physic Garden. He first practised in St Martin's Lane in a shop which, according to Woodward[60], was little more than a shed; from there he moved to Westminster, and it appears that at the age of twenty-one he had a practice in Covent Garden. He early experienced financial difficulties; indeed, it is stated that, at times, he was unable to provide himself with the bare necessities of life. His marriage with a dowerless maiden, Miss Travers, did not improve his prospects, and he sought to add to his income by the utilization of his botanical knowledge. He travelled over the country collecting plants, which he dried, put up into sets with descriptions and sold by subscription; also he arranged the collections and gardens of the Duke of Richmond and Lord Petrie. Hill soon found that Botany, from the monetary point of view, was unprofitable; he therefore decided to try his fortune on the stage, and appeared at the Haymarket and Covent Garden.

Woodward[61] gives a very amusing account of him in his new profession. After giving examples to shew Hill's limitations, he remarks: "There was a time at the celebrated Theatre of _May Fair_ he [Marr] represented _Altamont_, and the _Great Inspector_ [Hill] attempted _Lothario_; and the polite Audience of that Place all choruss'd and agreed with you, when you dying, said, 'O Altamont! thy Genius is the stronger.'... Can I forget, great Sir, your acting _Constant_, in the _Provok'd Wife_, and your _innocent_ Rape of Mrs Woffington; when, in a certain Passage, where, at least, a seeming Manliness was necessary, you handled her so awkwardly, that she joined the Audience in laughing at you."

Woodward's account may be accepted as being substantially correct, for in many ways Hill shewed that he lacked the qualities requisite for a successful career on the stage in those days.

Having thus failed as an actor, Hill returned to the practice of medicine and seemingly with more success, for in 1746 he was serving as a regimental surgeon, a position doubtless not very remunerative but helping to keep the wolf from the door. This same year saw the publication of Theophrastus's treatise on gems. In its new guise the value of the work was much enhanced since Hill intercalated much information that was lacking in the original; further, the work was so well executed that it gained him the attention and good-will of eminent Fellows of the Royal Society.

The publication of this work was probably the turning point in Hill's career, and its success must have influenced him not a little in the determination of following a literary career. In 1846 he edited the _British Magazine_, a periodical which lived but four years. His activities in this direction were phenomenal, and it is hard to realize how he managed to find time for so much work, for in addition to his botanical publications, which will be considered hereafter, he wrote on such diverse subjects as the art of acting, the conduct of married life, theology, naval history, astronomy, entomology, human anatomy and other medical subjects. Also he wrote an opera, two farces, and certain novels. Much of this output represents mere hack work, but it shews that Hill had an enormous capacity for work, indeed on one occasion when he was sick, he confessed to a friend that he had overtaxed his strength in writing seven works at the same time.

The _Dictionary of National Biography_ gives 76 titles of his publications, exclusive of eight which are generally attributed to him. Hill's output was probably even more extensive, for towards the latter part of his career he sometimes used to publish under a pseudonym. It is the more remarkable since he found time to enjoy the good things of the world, without which indulgence, according to his biographer[62], "he could not have undergone the fatigue and study inseparable from the execution of his vast designs." Again, according to Fitzgerald[63], he was "invariably in the front row at the theatres, exciting attention by his splendid dress and singular behaviour. When there was loud applause for the King, the doctor was seen to rise, and bow gravely to his Majesty."

The next few years were eventful ones for Hill. In 1751 he contributed a daily letter, called the _Inspector_, to the _London Advertiser and Literary Gazette_; although they came to an end in 1753, the Inspectors were highly remunerative, thus it is stated that in one year Hill profited to the extent of £1500 by their sale, a very large sum for journalistic work in those days. They thus brought him very prominently before the public, and incidentally proved a source of some trouble to him.

In connexion with the _Inspector_ justice has not been altogether done to Hill: no doubt, as Isaac Disraeli[64] states, that in them he retailed all the great matters relating to himself and all the little matters relating to others, but they were not all concerned in retailing the tales of scandal heard in the Coffee Houses and other places of public resort; nor were they always rendered palatable by these means as is stated in Rose's _Biographical Dictionary_[65]. They, in addition to comments and criticisms on current affairs, treated of many subjects. For instance, one considers the proposal for uniting the kingdoms of Great Britain and Ireland, another is a very sympathetic and laudatory review of Gray's _Elegy_, whilst a third treats of the art of embalming. Many are concerned with Natural History, and these are important as they shew Hill in another and very important character, namely that of a popular writer on Natural History, especially Botany. In one number he described the structure of a common flower, including an account of the movements of a bee in collecting pollen; and in another he described the appearance of microscopic organisms paying marked attention to their activities. These particular Inspectors are very pleasing and are well and clearly written; one especially is of outstanding importance, as it shews that Hill was in some respects far in advance of his times. He put forward a suggestion that Botany would be much improved by the delivery of public lectures in the museum with the living plants before the lecturer and the members of the audience. This scheme has yet to be carried out; as they are, museums are a means of education for the few, but a source of confusion to the many. For the latter their educative value would be enormously increased by the delivery of lectures illustrated by the exhibits, for the spoken word is more abiding than the printed label.

The methods of criticism pursued by Hill in the _Inspector_ soon involved him in controversy with various people. It is a difficult matter to appraise him in these respects; possibly his success had turned his head for, according to Baker[66], he shewed "an unbounded store of vanity and self-sufficiency, which had for years lain dormant behind the mask of their direct opposite qualities of humility and diffidence; a pride which was perpetually laying claim to homage by no means his due, and a vindictiveness which never could forgive the refusal of it to him." Baker then goes on to remark that as a consequence of this, every affront however slight was revenged by Hill by a public attack on the morals etc. of the maker.

On the other hand his criticisms may have been honest, at any rate in part; and the fact that they landed him into difficulties does not necessarily indicate that he was a dishonest fellow; most people are impatient of adverse criticism, and in those days such impatience found a vent in a pamphlet war or in personal violence. Nowadays the aggrieved manager, for instance, can shut his theatre doors against the distasteful critic; or, in other cases, an action for libel appears to be not altogether unfashionable.

_His attack on the Royal Society._

The real origin of Hill's attack on this learned society is somewhat obscure.

At the time of his death Chambers was engaged in the preparation of a supplement to his _Cyclopaedia_. The publishers then commissioned John Lewis Scott to prepare the work, but as Scott was soon afterwards appointed tutor to the royal princes it was entrusted to Hill. It is stated that the botanical articles were quite good, but that the more general parts were done with Hill's "characteristic carelessness and self-sufficiency." When the work was approaching completion the publishers considered that the title-page would look better if Hill had the right of adding F.R.S. after his name. He, in consequence, and, it is stated, contrary to the advice of Folkes, endeavoured to obtain the necessary qualification for candidature; but he was disliked to such an extent that he could not obtain the requisite number of signatures, three, for his certificate, notwithstanding the fact that the number of Fellows was about three hundred. This perhaps was hardly surprising since he had criticized his contemporary scientists very adversely, designating them by such terms as "butterfly hunters," "cockle shell merchants" and "medal scrapers." This reverse must have been a severe blow to his vanity, for there can be no doubt that his claims to the Fellowship, on scientific grounds, were as strong as any and stronger than those of most of the Fellows. And this Hill, who was by no means lacking in self-confidence, knew. His criticism of the Society culminated in his _Review of the Works of the Royal Society of London_ (1751)[67], which was in appearance like that of the _Transactions_, and consisted of reviews of several papers with comments by Hill. The work was dedicated to Martin Folkes, the President, on whom he placed the responsibility for publication, for, wrote he in his dedication, "The Purport of the more considerable of them has been long since delivered to you in conversation; and if you had thought the Society deserved to escape the Censure that must attend this Method of laying them before the World, you might have prevented it, by making the necessary Use of them in private.

"Nor is this, Sir, the only Sense in which you have been the great Instrument of their Production; since it cannot but be acknowledged, that if any body, except your great Self, had been in the high Office you so worthily fill at present, the Occasions of many of the more remarkable of them could not have been received by the Body, under whose Countenance alone they claim their Places in this Work."

He then charges Folkes with unworthy conduct towards him, and, in brief, he considered that Folkes and Baker were his enemies. The reason for this, according to Hill, was as follows. An eminent French correspondent had taxed him, supposing him to be a Fellow, with "one of the errors of the Society"; Hill in reply wrote, "I have already set right the error you complain of; but you are to know, that I have the Honour not to be a Member of the Royal Society of London." Before he had sealed this letter he was called out of the room, and before he had returned a visitor, a Fellow of the Society, was shown into Hill's study and read the letter containing the above-quoted passage. Hence the friction. Hill denies that he ever became a candidate for election, and states that although he attended the meetings he would not become a member on account of the Society's method of performing that which they were founded to do.

These statements are not lacking in definition; with regard to the incident of the letter it is impossible to judge of the truth; but with regard to the main features of the controversy the present writer thinks it extremely probable that the account first given is substantially correct, notwithstanding the statement that Hill's explanation was never contradicted[68].

As regards the _Review_, Hill wrote that "he pretends to nothing but the knowing more than the Royal Society of London appears by its publications to know! and surely a Man may do that and yet be very ignorant!"

The intention of the _Review_ was to point out to the Society its shortcomings, doubtless in order that it might reform itself.

There can be no doubt whatever that a candid critic was necessary, for some of the papers were absolute rubbish, so much so indeed that a scientific training does not appear necessary to detect their futility. To take a brief example; in one paper the author describes a method to make trees grow very large; the seeds are to be sown at the absolute moment of the entry of the sun into the vernal equinox, and then to transplant them at the moment when the moon is full.

Hill himself sometimes falls into error in his criticisms; thus he adversely comments on the truth of the power of cobwebs to catch thrushes[69].

At the beginning of Part VII of his _Review_, which treats of plants, he thrusts very deep. He says, "This is a Branch of Natural Knowledge, which, it will appear, that the Royal Society of London have looked so very deeply into, that their rejecting the Linnean System of Botany, when offered by its Author will no longer be wondered at."

In this Part he is particularly severe upon Baker, and, in reading it, one is forced to the conclusion that although adverse criticism was warranted, there was a good deal of personal feeling behind it.

This attack on the Royal Society appears to have been much resented, and Hill's credit consequently was much damaged, for it was considered that Folkes and Baker had befriended him in his earlier days. With regard to Folkes it has been seen that Hill considered that he was doing a public duty; and with regard to Baker, Hill suffered under a real or imaginary grievance which, assuming Baker had helped him in the past, cancelled all obligations due from him to Baker. If this be not so then Hill, in addition to his other faults, was lacking in gratitude. With regard to this point his anonymous biographer[70] wrote that "we have nowhere learnt that ingratitude had the smallest share in the composition of the character of Sir John Hill."

The attack, however, was not altogether fruitless, as Disraeli[71] remarks, "Yet Sir John Hill, this despised man, after all the fertile absurdities of his literary life, performed more for the improvement of the Philosophical Transactions, and was the cause of diffusing a more general taste for the science of botany, than any other contemporary."

It is hardly necessary to remark that Hill was never elected to the Royal Society.

* * * * *

Thus by his methods of criticism Hill brought to an end a period of highly remunerative literary work; it was therefore necessary for him to seek other pastures. He returned, in part, to the practice of medicine in the shape of herbalist, preparing remedies from various plants such as valerian, water-dock and centaury; also he wrote on the virtues of these and other plants. The source from which he obtained his plants was in the first instance the Chelsea Physic Garden, but it is stated that he was eventually forbidden its use owing to his depredations; later he grew the requisite plants in his own garden which was situated where now is Lancaster Gate. There was a good deal of common sense in his remedies; thus in his _Virtues of British Herbs_ he remarks that "He who seeks the herb for its cure, will find it half effected by the walk."

By the sale of his medicines and of his pamphlets relating to medicinal plants, some of which ran through many editions, he made large sums of money.

Before passing on to a consideration of Hill's botanical work brief comment may be made on his literary activities other than those already alluded to. It has already been mentioned that much of his output represented mere hack work, so that it is not surprising to learn, in view of the large amount of work he did, that a certain proportion of it was careless and slovenly, and shewed marked signs of undue haste in production, with the result that his reputation suffered. One work, entitled _Letters from the Inspector to a Lady with the genuine Answers_ (1752), is an amorous correspondence not remarkable for its reticence of statement; it reminds one of a similar, but more proper, correspondence, which had a vogue a few years ago.

Hill did not always write for gain, thus _Thoughts concerning God and Nature_ (1755) shews him in a different light. This was written from conscientious and religious motives in answer to a book written by Henry St John Viscount Bolingbroke, and was published at a loss, for the number printed, even if all were sold, would not have paid the expenses of production.

His dramatic pieces were of a mediocre nature, and with regard to his novels and other works Baker[72] states that "In some parts of his novels incidents are not disagreeably related, but most of them are nothing more than narratives of private intrigues, containing, throughout, the grossest calumnies, and aiming at the blackening and undermining the private characters of many respectable and amiable personages. In his essays, which are by much the best of his writings, there is, in general, a liveliness of imagination, and a prettiness in the manner of extending perhaps some very trivial thought; which, at the first _coup-d'œil_, is pleasing enough, and may, with many, be mistaken for it; but, on a nearer examination, the imagined sterling will be found to dwindle down into mere French plate."

In addition to his literary work Hill found time to undertake official duties. In 1760 he was gardener at Kensington Palace, a post which brought him in an income of £2000 per annum[73]; also he was Justice of the Peace for Westminster. According to Mrs Hill[74] he was nominated Superintendent of the Royal Gardens, Kew, and as such he is described on his portrait; his nomination, however, does not appear to have been confirmed, for Thiselton-Dyer[75] states that there is no evidence of his ever having occupied such a position. Hill also advised, at the request of the Earl of Bute, the governors of various islands regarding their cultivation, for which work he received no remuneration[76].

_Anatomy._

Anatomical investigations during the eighteenth century were very barren of results, no real advance upon the discoveries of Grew, Malpighi and others being made. The work of Hill in this field forms no exception to this statement; and, although he accomplished a fair amount of anatomical work, his investigations apparently were without result in the advancement of this particular branch of knowledge.

In 1770 Hill published a small octavo volume on _The Construction of Timber_. In order that other investigators might benefit from his experience he fully described and figured the instruments used; of particular interest is a small hand microtome with which he cut his sections. This ingenious tool was the invention of Cummings, and does not differ in essentials markedly from some the writer has seen in use; Hill claims that when the cutter was particularly sharp sections no thicker than a 2000th part of an inch could be obtained. The microscope was made by Adams under the direction of Hill and his patron, unnamed in the book, but in all probability Lord Bute, and embodied some improvements on earlier instruments. This microscope is figured in Carpenter's work on _The Microscope and its Revelations_[77].

The _Construction of Timber_ is well arranged: the work begins with a general description of the tissues and their disposition in a thickened stem; then follows a more detailed account of the separate tissues; and finally much space is devoted to a comparison of different tissues in various plants.

Hill's account is fully illustrated with copper plates; his figures of sections are not highly magnified, some not more than twelve times, and their quality is not equal to the best in Grew's _Anatomy_.

Hill principally studied transverse sections, and consequently fell into errors which he might have avoided by the careful observation of longitudinal ones; also he used macerated material, but as his method preserved only the stronger walled elements he did not gain to any great extent from their use.

The parts devoted to comparative anatomy are not at all bad, and they give a concrete idea of the differences obtaining in the different plants.

He apparently understood the nature of the annual rings, and of them he wrote as follows: "These are the several coats of Wood, added from season to season. It has been supposed that each circle is the growth of a year; but a careful attention to the encrease of wood has shewn me, beyond a doubt, that two such are formed each year; the one in the Spring, the other soon after Midsummer." His illustration, however, is not so clear as his statement. Also he realized that the wood vessels were in some way connected with water:

"These vessels arise in the substance of the Wood, principally towards the outer edge of each circle. They are very large in the outermost coat; and smaller in the others: and there are also irregular ranges of them, running thro' the thicknesses of the circles; besides these principal ones of the outer course. They have solid, and firm, coats; and they contain in Spring, and at Midsummer, a limpid liquor, like water, but with a slight acidity: at all other seasons of the year they appear empty, their sides only being moistened with the same acid liquor. Those who examined them at such seasons, thought them air vessels; and in that opinion, formed a construction for them, which Nature does not avow."

Although Hill recognized the entity of the cell he had, in common with his contemporaries, no clear conception of its real nature.

In describing the pith of the rose he does not go astray, and he fully appreciated that the seemingly double contour of the cell walls, when seen in some sections, is due to the thickness of the section with consequent overlapping of the cells; on the other hand he went very wrong in the case of the pith of the walnut, the cavities of which he supposed to be cells like those of the rose, only very much larger and uniseriate as the following quotation shews:

"The Pith of the Walnut consists only of one range of these bladders ['Blebs' or cells], smaller at the edges, largest in the middle, and laid very exactly one upon the other."

When he considers the structure of more or less square or oblong cells his ideas are very wrong. In such cases he thought that the transverse walls were spaces, and the longitudinal walls vessels; curiously enough Hedwig made a similar mistake some years later, possibly he was led astray by Hill's misconception.

Hill adversely criticized the theory that the pith is an organ of propagation, and substituted the view that the corona--i.e. the peri-medullary zone--is all important in this connexion, "From it arises the branches, and encrease of the tree."

Hill had considerable technical ability and, I think, was capable of greatly advancing anatomical botany; unfortunately, however, he gave too little time and thought to his investigations.

_Physiology._

The eighteenth century saw the birth of vegetable physiology, Hales and Knight being the two great pioneers in this country. The former flourished in the early part of the century, whilst Knight, although born in 1758, published his great work in 1806.

The chief physiological work of Hill is embodied in a pamphlet of 59 pages, entitled _The Sleep of Plants and Causes of Motion in the Sensitive Plant explain'd_, published in London in 1757, a year previous to the appearance of Du Hamel's _Physique des Arbres_. The paper is in the form of a letter to Linnaeus, and in it the author explains his position with regard to his earlier criticisms of the Linnaean system of classification.

The work is divided into sections, the first of which consists of a brief historical _resumé_, the opinions of Acosta, Alpinus, Ray and Linnaeus on this subject being alluded to. No mention, however, is made of the observations of Bonnet and of Mairan to the effect that the periodic movements of _Mimosa pudica_ continued when the plant was kept in prolonged darkness.

In Section 2, after describing the structure of a leaf, Hill remarks that "Leaves are always surrounded by the air; and they are occasionally and variously influenced by heat, light, and moisture. They are naturally complicated, and they act on most occasions together. We are therefore to observe, first, what effects result from their mutual combinations in a state of nature: and having assigned in these cases the effect to the proper and particular cause, from this power of that agent, whichsoever it is, that acts thus in concert with the rest, we may deduce its operations singly."

This passage, although not particularly clear, indicates that Hill fully appreciated the fact that the reaction exhibited by a plant organ is a response to the resultant of a number of forces, and that each factor must be examined separately.

He then goes on to describe his observations on _Abrus_; the structure of the leaf, more especially the course of the vascular bundles, is first dealt with, and then an explanation of the action of light is given. Needless to say, in view of the state of physical science at this period, his explanation, although ingenious, is wide of the mark. He wrote that "Light is subtile, active, and penetrating: by the smallness of its constituent parts, it is capable of entering bodies; and by the violence of its motion, of producing great effects and changes in them. These are not permanent, because those rays which occasion them, are, in that very action, extinguished and lost.

"Bodies may act on light without contact; for the rays may become reflected when they come extreamly near: but light can act on bodies only by contact; and in that contact the rays are lost. The change produced in the position of the leaves of plants by light, is the result of a motion occasioned by its rays among their fibres: to excite this motion, the light must touch those fibres; and where light touches, it adheres, and becomes immediately extinguished.... The raising of the lobes in these leaves will be owing to the power of those rays which at any one instance fall upon them: these become extinguished; but others immediately succeed to them, so long as the air in which the plants stands, is enlightened."

Although it was not until 1822, when Dutrochet pointed out the true significance of the pulvini, Hill recognized that these structures were concerned with the movements of the leaflets, not only in the case of _Abrus_, but also in _Mimosa_. He remarked that "It is on the operation of light upon these interwoven clusters of fibres [which are placed at the bases of the main rib, and of the several foot-stalks of the lobes], that the motion of the leaves in gaining their different positions depends; and consequently, the motion itself is various according to the construction of these fibres.

"In the Abrus they are large, and of a lax composition; consequently the lobes are capable of a drooping, an horizontal, and an oblique upward position: in the Tamarind, and the broad-leaved Robinia, they are more compact, and hence all the motion of which those leaves are capable, is an expanding open and a closing sideways; which the direction and course of the fibres also favours: in the Parkinsonia they are smaller, and yet more compact; and the consequence of this is, that its lobes have no farther possible motion, than the expanding upwards."

Again, "The clusters of fibres are as a kind of joints on which their lobes are capable, under the influence of light, of a certain limited motion."

Further, with regard to _Mimosa_, he remarks that "To propagate the motion when the leaves are in a state to shew it, there requires a perfect and confirmed state of those clusters of fibres lodged at their base." Hill then describes the experiments upon which he based his conclusions; these shew that he was fully awake to the importance of keeping the conditions of an experiment, other than those of light, as near constant as possible, and that the position assumed by the leaves depends upon the intensity of the light.

His final experiment was to place the _Abrus_ in a bookcase in such a position that the sun shone full upon it; when the leaves were fully expanded he closed the doors and found that in an hour "The lobes were all drop't, and it was in the same state that it would have shewn at midnight. On reopening the doors the elevated position of the leaves was assumed in twenty minutes."

Hill offers the same explanation of the movements of _Mimosa_ as of those exhibited by _Abrus_, the reason for their greater conspicuousness in the former plant being due to the fact that in _Mimosa_ "As there are no less than three sets of these clusters [of fibres which are placed at the bases of the foot-stalks], the effects of the same principle are naturally much greater than in the Abrus where there is only one."

Hill carefully observed the sequence of motion in the _Mimosa_, and points out that the effect of absolute darkness on the plant is greater than the rudest touch. He also found that the contact stimulus must be of a sufficient intensity, and that the degree of the subsequent motion depended upon the potency of the stimulus. He further observed that shaking the plant had the same effect as contact stimulation; also he remarks upon the fact that the movements of the _Mimosa_ and of the Tamarind are less well-marked at a temperature lower than that in which the plants have been reared. Hill considered that "This is probably due to the juices stagnating in the clusters of fibres, and to the contraction of the bark by cold." His explanation of the response to the contact stimulus is of course quite wrong; it may, however, be quoted as an illustration of the view, current at that time, that such motion was due to the fibres which acted like those of muscle. "The vibration of the parts is that which keeps the leaves of the sensitive plant in their expanded and elevated state: this is owing to a delicate motion continued through every fibre of them. When we touch the leaf, we give it another motion more violent than the first: this overcomes the first: the vibration is stopped by the rude shock: and the leaves close, and their foot stalks fall, because that vibrating motion is destroyed, which kept them elevated and expanded.... That the power of motion in the sensitive plant depends upon the effect of light on the expanded surface of the leaves, is certain; for till they are expanded, they have no such power. The young leaves, even when grown to half an inch in length have no motion on the touch, tho' rough and sudden."

Hill fully appreciated the importance of comparative observations; he compared the movements, in response to light, of _Abrus_ and _Mimosa_, which plants he placed side by side so that the conditions of the experiment might be the same for each. He found that "In these and in all others, the degree of elevation or expansion in the lobes, is exactly proportional to the quality of the light: and is solely dependent upon it."

Reference also may be made to Hill's views on reproduction[78]; he considered that the pollen grain contained the embryo which was set free by the bursting of the grain after it had been deposited upon the stigma. The stigmatic hairs or papillae were supposed to be the ends of tubes into which the embryos entered, made their way into the placenta, and thus arrived into the "shells of the seeds" (the ovules). It is unnecessary to point out the absurdities of these ideas, but it may be mentioned that Hill's interpretations of his observations were at fault rather than the observations themselves. Thus, judging from his figures, he saw the contents of the pollen grain, the appearance of which, under the conditions of observation, might easily suggest the idea of an embryo. Also he noticed that the pollen grains burst in a little while when placed in water, a phenomenon which was rediscovered 138 years later[79], and he therefore thought that a similar bursting, with a consequent setting free of the embryo, would take place on the wet stigma of the lily, for example.

_Taxonomy._

One of Hill's more interesting works in this branch of Botany is his _British Herbal_[80]. In it are described a large number of plants which are illustrated by 75 copper plates engraved by various artists. None of these plates are of outstanding excellence, indeed many of them are very poor, and their quality is uneven. Those in the folio consulted by the present writer were ruined by being coloured.

The plants described are arranged on a system which is not altogether without interest as it, in a small degree, foreshadows later systems. It may be indicated by giving the characters of the first four classes.

Class 1. Plants whose flower consists of several petals, with
numerous threads in the center, and is followed by a cluster of
naked seeds.

Class 2. Plants whose flower consists of several petals, with
numerous threads in the center, and whose seeds are contained in
several pods.

Class 3. Plants whose flower consists of a single petal, and is
succeeded by several capsules.

Class 4. Plants with the flower formed of a single petal, plain,
and of a regular form and succeeded by a single capsule.

It will be seen that Hill relied much on the characters of the corolla and the gynaeceum. But the chief interest in this work is, perhaps, Hill's criticisms of Linnaeus. One example will suffice; Linnaeus is criticised for placing _Myosurus_ among the pentandria polygynia and thus separating it from _Ranunculus_, _Adonis_, etc. Hill remarked that thus to separate these plants merely because the number of stamens in _Myosurus_ is less than in _Ranunculus_ is unreasonable since they agree in all other essentials. He himself, however, made a similar error, for it will be observed that in the system followed in the Herbal, _Ranunculus_ falls into the first class and _Helleborus_ into the second.

These criticisms of Linnaeus, however, are not all of an adverse nature; in many places Hill does not stint his praise; and he does not fail, after describing each Genus, to mention its position in the Linnaean System.

Pulteney[81] found it difficult "to reconcile the praises this author bestows on Linnaeus, in many of his writings, with the censures contained in his British Herbal." The difficulty is not very apparent; Hill sufficiently indicated his position in the following passage taken from the _Sleep of Plants_. "If our opinions have differed, 'tis upon a single Point; your arrangement of plants. In regard to that much greater article, the establishing their distinctions, and ascertaining their characters, I have always admired and reverenced you: to dispute your determinations there, were to deny the characters of nature.

"Free in the tribute of applause on this head, I have on the other been as open in my censures; equally uninfluenced by envy, and by fear. It is thus science may be advanced; and you will permit me to say, thus men of candour should treat one another."

Linnaeus is also criticised in the _Vegetable System_, more particularly for his unnecessary introduction of new names for plants; but here again Hill is full of praises for Linnaeus's descriptions of species.

Although opposed to the Linnaean system Hill recognised its value as a means of evolving order out of chaos, and to him falls the credit of introducing it into England. Its first introduction was in his _History of Plants_ (1751), but it was unsatisfactory since the _Species Plantarum_ was not published until 1753. Hill next explained it in 1758[82], but it was not until two years later that the first _British Flora_, arranged on this system, appeared[83]. According to Pulteney[84], Hill performed this task "in a manner so unworthy of his abilities, that his work can have no claim to the merit of having answered the occasion: and thus the credit of the atchievement fell to the lot of Mr William Hudson F.R.S."