Chapter IV: Franklin as a Man of Science (3)

Some years after the publication of this essay, Franklin devised an improvement in the open chimney-place which tended to abate drafts and check the escape of heat up the chimney by contracting the chimney opening, bringing its breast down to within three feet of the hearth, and placing an iron frame just under this breast, with grooves on each side of the frame, in which an iron plate could be slid backwards and forwards at pleasure, for the purpose of cutting off the mouth of the chimney entirely from the chimney itself, when there was no fire on the hearth, or of leaving a space of not more than two inches for the escape of smoke between the further edge of the plate and the back of the chimney-mouth. This improved chimney-place was described by Franklin in letters to Alexander Dick and James Bowdoin. The letter to Bowdoin seems to leave little to be said on the subject of chimneys. It indicates that Franklin had subjected them to a scrutiny hardly less close than that which he had fixed upon the Leyden Jar. In connection with the currents and reverse currents, set up in them in summer by the relations of inequality, which the air in them sustains, at different hours of the day and night, to the outside temperature, he suggests that joints of meat might keep for a week or more during the hottest weather in chimney-openings, if well wrapt three or four fold in wet linen cloths, sprinkled once a day with water to prevent evaporation. Butter and milk in vessels and bottles covered with wet cloths might, he thought, be preserved in the same way. And he even thought, too, that the movements of air in chimneys might, with the aid of smoke-jack vanes, be applied to some mechanical purposes, where a small but pretty constant power only was needed. To appreciate how patiently and exhaustively Franklin was in the habit of pursuing every course of observation or reflection opened up by his scientific propensities, the whole of this letter, which had much more to say on the subject of chimneys than we have mentioned, should be read.

At a later period of his life, Franklin describes to Turgot what he called his new stove. The novel feature of this consisted of an aerial syphon by which the smoke from the fireplace of the stove was first drawn upwards through the longer leg of the syphon, and then downwards through its shorter leg, and over burning coals, by which it was kindled into flame and consumed.

The ingenuity of Franklin was also exerted very successfully in the rectification of smoky chimneys. In his essay on the causes and cure of such chimneys, written on his last ocean voyage, he resolved the causes into no less than nine heads, and stated with his accustomed perspicuity and precision the remedy for each cause. In his time, the art of properly carrying off smoke through chimneys was but imperfectly understood by ordinary builders and mechanics, and it was of too humble a nature to tempt discussion by such men of science as were capable of clearly expounding the physical principles upon which it rested. It was not strange, therefore, that Franklin, who deemed nothing, that was useful, to be beneath the dignity of philosophy, should have acquired in his time the reputation of being a kind of "universal smoke doctor" and should have been occasionally consulted by friends of his, such as Lord Kames, about refractory chimneys. The only smoky chimney, that seems to have completely baffled his investigation, recalls in a way the philosopher, who thought that he had discovered a new planet, but afterwards found that what he saw was only a fly in the end of his telescope. After exhausting every scientific resource in an effort to ascertain why the chimney in the country-house of one of his English friends smoked, Franklin was obliged to own the impotence for once of his skill; but, subsequently, his friend, who made no pretensions to the character of a fumist, climbed to the top of the funnel of his chimney by a ladder, and, on peering down into it, found that it had been filled by nesting birds with twigs and straw, cemented with clay, and lined with feathers.

Nor was the attention given by Franklin to ventilation by any means confined to chimneys. Air vitiated by human respiration also came in for a share of it. Describing an experiment by which he demonstrated the manner in which air affected in this way is purified, Alexander Small said:

The Doctor confirmed this by the following experiment.
He breathed gently through a tube into a deep glass
mug, so as to impregnate all the air in the mug with
this quality. He then put a lighted bougie into the
mug; and upon touching the air therein the flame was
instantly extinguished; by frequently repeating the
operation, the bougie gradually preserved its light
longer in the mug, so as in a short time to retain it
to the bottom of it; the air having totally lost the
bad quality it had contracted from the breath blown
into it.

Franklin became deeply interested in the brilliant course of investigation pursued by Priestley with respect to gases, and several penetrating glances of his into the relations of carbonic acid gas to vegetation have come down to us. Observing on a visit to Priestley the luxuriance of some mint growing in noxious air, he suggested to Priestley that "the air is mended by taking something from it, and not by adding to it." He hoped, he said in a letter to Priestley, that the nutriment derived by vegetation from carbonic acid gas would give some check to the rage of destroying trees that grew near houses, which had accompanied recent improvements in gardening from an opinion of their being unwholesome.

Just as he was consulted about the best methods of protecting St. Paul's Cathedral and the arsenals at Purfleet from lightning, so he was also consulted by the British Government as to the best method for ventilating the House of Commons. "The personal atmosphere surrounding the members," he thought, "might be carried off by making outlets in perpendicular parts of the seats, through which the air might be drawn off by ventilators, so placed, as to accomplish this without admitting any by the same channels." The experiment might be tried upon some of our City Councilmen. Principles of ventilation, expounded by Franklin, were also utilized by the Messrs. Adam of the Adelphi, in the construction of the large room built by them for the meetings of the Society for the Encouragement of Arts. We also find him suggesting openings, close to the ceilings of rooms, and communicating with flues, constructed alongside of chimney flues, as effective means for ventilating rooms.

With all his primary and secondary gifts for scientific research, it is difficult to believe that, if Franklin had not been diverted from it by engrossing political cares, he would have added both to his special reputation as a student of electricity and to his general reputation as a man of science. As it was, his civic activity and popular leadership in Pennsylvania, his several agencies abroad, his participation in the American Revolution, his career as Minister to France, and his official duties, after his return, made such imperious demands upon his time that he had little or no leisure left for scientific pursuits. This picture of his situation which he presented in a letter to Ingenhousz, when he was in France, was more or less true of almost every part of his life after he became famous:

Besides being harass'd with too much Business, I am
expos'd to numberless Visits, some of Kindness and
Civility, many of mere idle Curiosity, from Strangers
of America & of different Parts of Europe, as well as
the Inhabitants of the Provinces who come to Paris.
These devour my Hours, and break my Attention, and at
Night I often find myself fatigu'd without having done
anything. Celebrity may for a while flatter one's
Vanity, but its Effects are troublesome. I have begun
to write two or three Things, which I wish to finish
before I die; but I sometimes doubt the possibility.

Some of the reflections of Franklin on scientific subjects, such as his early letters to Cadwallader Colden with regard to "perspirants and absorbents" are, to use his own expression in one of them, too plainly _ultra crepidam_ to have any value. Of others, we might fairly say that his knowledge of the topics which he handled in them was hardly deep enough to deserve any praise more confident than that which he allowed himself when writing to Cadwallader Colden in 1751 of the Philadelphia Experiments. "So," he said to Colden in this letter, "we are got beyond the skill of _Rabelais's_ devils of two years old, who, he humorously says, had only learnt to thunder and lighten a little round the head of a cabbage." All the same, even aside from his electrical experiments, Franklin acquired no little fame as a philosopher, made more than one fruitful suggestion to fellow-workers of his in the domain of science and contributed many useful observations to the general fund of scientific thought.

Apparently his views on medical topics were held in very considerable respect. In 1777, he was elected a member of the Royal Medical Society of Paris, and in 1787 an honorary member of the Medical Society of London. Many works on medical subjects were dedicated to him by their authors. He was one of the commission which exposed the imposture of Mesmer. There are few things that give us a better idea of the extraordinary celebrity enjoyed by him than the wide currency obtained by a spurious opinion of his, ascribing great merit to tobacco ashes as a remedy for dropsy. It won such an extensive circulation, and brought down on his head such a flood of questions from physicians and others, that he was compelled to deny flatly the truth of the story. One person, Lord Cadross, afterwards the Earl of Buchan, firmly believed that he would have perished at the hands of a professional physician, who wished to blister him, when he was afflicted with a fever, if Franklin had not dissented from the treatment. Franklin probably deserved no higher credit for his dissent on this occasion than that of sharing the opinion of Sir John Pringle, who was convinced that, out of every one hundred fevers, ninety-two cured themselves. So far as we can see, there is nothing in the works of Franklin to warrant the belief that he possessed any uncommon degree of medical knowledge, though he was full of curiosity with regard to medicine as with regard to every other branch of human learning. In one of his letters to Colden, written in his fortieth year, he expressed the hope that future experiment would confirm the idea that the yaws could be cured by tar-water. In a later letter to Colden, he expressed his pleasure at hearing more instances of the success of the poke-weed "in the Cure of that horrible Evil to the human Body, a Cancer." At his suggestion, a young physician, with the aid of Sanctorius' balance, tested alternately each hour, for eight hours, the amount of the perspiration from his body, when naked, and when warmly clad, and found that it was almost as great during the hours when he was naked. By his investigations into the malady known in his time popularly as "the dry bellyache," and learnedly as the "_colica Pictonum_," he conferred a real benefit upon medical science. His views upon the subject received the honor of being incorporated with due acknowledgments into Dr. John Hunter's essay on the _Dry Bellyache of the Tropics_. Summarily speaking they were that the complaint was a form of lead poisoning.

I have long been of opinion [he wrote to Dr.
Cadwallader Evans in 1768] that that distemper proceeds
always from a metallic cause only; observing that it
affects, among tradesmen, those that use lead, however
different their trades,--as glaziers, letter-founders,
plumbers, potters, white-lead makers, and painters;...
although the worms of stills ought to be of pure tin,
they are often made of pewter, which has a great
mixture in it of lead.

The year before this letter was written, Franklin had found on reading a pamphlet, containing the names and vocations of the persons, who had been cured of the colic at Charite, a Parisian hospital, that all of them had followed trades, which handle lead in some form or other. On going over the vocations, he was at first puzzled to understand why there should be any stonecutters or soldiers among the sufferers, but his perplexity was cleared up by a physician at the hospital, who informed him that stonecutters frequently used melted lead for fixing the ends of iron balustrades in stone, and that the soldiers had been employed as laborers by painters, when grinding colors. These facts were long afterwards communicated by Franklin to Benjamin Vaughan in a letter, in which he cited other incidents, interesting partly because they corroborated his theory, and partly because they are additional proofs of his vigilance and patience in collecting facts, before advancing an hypothesis, as well as of a memory, which retained every instructive circumstance imparted to it by eye or ear as imperishably as hardening cement retains the impression of a dog's foot. When he was a boy at Boston, Franklin said, it was discovered that New England rum, which had produced the dry bellyache and paralyzed the limbs in North Carolina, had been made by distilleries with leaden still-heads and worms. Later, when he was in London, he had been warned by an old workman at Palmer's printing-house, as well as by an obscure pain in his own hands, that it was a dangerous practice to handle a heated case of types. About the same time, a letter-founder in the same close at Palmer's, in a conversation with him, ascribed the existence of the ailment among his workmen to the fact that some of them were slovenly enough to go to their meals with unwashed hands that had come into contact with molten lead. He had also observed in Derbyshire that the smoke from lead furnaces was pernicious to grass and other vegetables, and in America had often observed that streaks on shingle roofs, made by white lead, washed from balusters or dormer window frames, were always entirely free from moss. He had also been told of a case where this colic had afflicted a whole family, and was supposed to be due to the corrosive effect of the acid in leaves, shed upon the roof, from which the family derived the supply of rain water, upon which it relied for drink.

More important still than the insight that Franklin obtained into the Painter's Colic was the insight which he obtained into the salutary effect of the custom which is now almost universal, except in the homes of the ignorant and squalid, of sleeping at night in rooms with the windows up. This custom, as well as the outdoor regimen, which has proved of such signal value in the treatment of tuberculosis, originated in hygienic conceptions identical with those steadfastly inculcated by him. His opinions with regard to colds and the benefits of pure air were expressed at many different times, and in many different forms, but nowhere so conveniently for the purposes of quotation as in a letter which he wrote to Dr. Benjamin Rush in 1773.

I hope [he said in this letter] that after having
discovered the benefit of fresh and cool air applied to
the sick, people will begin to suspect that possibly it
may do no harm to the well. I have not seen Dr.
Cullen's book, but am glad to hear that he speaks of
catarrhs or colds by contagion. I have long been
satisfied from observation, that besides the general
colds now termed _influenzas_ (which may possibly
spread by contagion, as well as by a particular quality
of the air), people often catch cold from one another
when shut up together in close rooms, coaches, &c., and
when sitting near and conversing so as to breathe in
each other's transpiration; the disorder being in a
certain state. I think, too, that it is the frouzy,
corrupt air from animal substances, and the perspired
matter from our bodies, which being long confined in
beds not lately used, and clothes not lately worn, and
books long shut up in close rooms, obtains that kind of
putridity, which occasions the colds observed upon
sleeping in, wearing, and turning over such bedclothes,
or books, and not their coldness or dampness. From
these causes, but more from too full living, with too
little exercise, proceed in my opinion most of the
disorders, which for about one hundred and fifty years
past the English have called _colds_.

As to Dr. Cullen's cold or catarrh _a frigore_, I
question whether such an one ever existed. Travelling
in our severe winters, I have suffered cold sometimes
to an extremity only short of freezing, but this did
not make me _catch cold_. And, for moisture, I have
been in the river every evening two or three hours for
a fortnight together, when one could suppose I might
imbibe enough of it to _take cold_ if humidity could
give it; but no such effect ever followed. Boys never
get cold by swimming. Nor are people at sea, or who
live at Bermudas, or St. Helena, small islands, where
the air must be ever moist from the dashing and
breaking of waves against their rocks on all sides,
more subject to colds than those who inhabit part of a
continent where the air is driest. Dampness may indeed
assist in producing putridity and those miasmata which
infect us with the disorder we call a cold; but of
itself can never by a little addition of moisture hurt
a body filled with watery fluids from head to foot.

Franklin's belief that colds and overeating often went hand in hand also found expression in one of his letters to Polly Stevenson. When sending her an account of some seamen, who had experienced considerable relief from thirst by wearing clothes kept constantly wet with salt water, he said, "I need not point out to you an Observation in favour of our Doctrine, that you will make on reading this Paper, that, _having little to eat_, these poor People in wet Clothes Day and Night _caught no cold_." In every, or in practically every, case, he seems to have referred colds to what he rather vaguely calls a siziness and thickness of the blood, resulting from checked perspiration, produced by different agencies, including a gross diet.

Thus [he says in his _Notes and Hints for Writing a
Paper Concerning what is called Catching Cold_], People
in Rooms heated by a Multitude of People, find their
own Bodies heated; thence the quantity of perspirable
Matter is increased that should be discharged, but the
Air, not being changed, grows so full of the same
Matter, that it will receive no more. So the Body must
retain it. The Consequence is, the next Day, perhaps
sooner, a slight putrid Fever comes on, with all the
Marks of what we call a Cold, and the Disorder is
suppos'd to be got by coming out of a warm Room,
whereas it was really taken while in that Room.

He did not shrink from any of the consequences of his reasoning about colds however extreme.

Be so kind as to tell me at your leisure [he wrote to
Barbeu Dubourg], whether in France, you have a general
Belief that moist Air, and cold Air, and damp Shirts or
Sheets, and wet Floors, and Beds that have not lately
been used, and Clothes that have not been lately worn,
and going out of a warm Room into the Air, and leaving
off a long-worn Wastecoat, and wearing leaky Shoes, and
sitting near an Open Window, or Door, or in a Coach
with both Glasses down, are all or any of them capable
of giving the Distemper we call _a Cold_, and you _a
Rheum, or Catarrh_? Or are these merely _English_
ideas?

His views on the wholesomeness of fresh air were far in advance of the general intelligence of his time, and were expressed in spirited terms. After stating in a letter to Jean Baptiste Le Roy that he had become convinced that the idea that perspiration is checked by cold was an error as well as the idea that rheum is occasioned by cold, he added:

But as this is Heresy here, and perhaps may be so with
you, I only whisper it, and expect you will keep my
Secret. Our Physicians have begun to discover that
fresh Air is good for People in the Small-pox & other
Fevers. I hope in time they will find out that it does
no harm to People in Health.

At times his language on what he called _aerophobia_ grew highly animated.

What Caution against Air [he said in a letter to Thomas
Percival], what stopping of Crevices, what wrapping up
in warm Clothes, what shutting of Doors and Windows!
even in the midst of Summer! Many London Families go
out once a day to take the Air; three or four Persons
in a Coach, one perhaps Sick; these go three or four
Miles, or as many Turns in Hide Park, with the Glasses
both up close, all breathing over & over again the same
Air they brought out of Town with them in the Coach
with the least change possible, and render'd worse and
worse every moment. And this they call _taking the
Air_.

Indeed, there is at times something just a little ludicrous in the uncompromising fervor with which Franklin insisted upon his proposition. It seemed strange he said, in the letter from which we have just quoted, that a man whose body was composed in great part of moist fluids, whose blood and juices were so watery, and who could swallow quantities of water and small beer daily without inconvenience, should fancy that a little more or less moisture in the air should be of such importance; but we abound in absurdity and inconsistency.

It is a delightful account that John Adams gives us of a night which he spent in the same bed with Franklin at New Brunswick, on their way to the conference with Lord Howe:

The chamber [Adams tells us] was little larger than the
bed, without a chimney, and with only one small window.
The window was open, and I, who was an invalid, and
afraid of the air in the night, shut it close. "Oh!"
says Franklin, "don't shut the window, we shall be
suffocated." I answered I was afraid of the evening
air. Dr. Franklin replied, "The air within this chamber
will soon be, and indeed is now, worse than that
without doors. Come, open the window and come to bed,
and I will convince you. I believe you are not
acquainted with my theory of colds." Opening the window
and leaping into bed, I said I had read his letters to
Dr. Cooper, in which he had advanced that nobody ever
got cold by going into a cold church or any other cold
air, but the theory was so little consistent with my
experience, that I thought it a paradox. However, I had
so much curiosity to hear his reasons, that I would run
the risk of a cold. The Doctor then began a harangue
upon air and cold, and respiration and perspiration,
with which I was so much amused that I soon fell
asleep, and left him and his philosophy together; but I
believe they were equally sound and insensible within a
few minutes after me, for the last words I heard were
pronounced as if he was more than half asleep. I
remember little of the lecture, except that the human
body, by respiration and perspiration, destroys a
gallon of air in a minute; that two such persons as we
were now in that chamber would consume all the air in
it in an hour or two; that by breathing over again the
matter thrown off by the lungs and the skin, we should
imbibe the real cause of colds, not from abroad, but
from within.

At times Franklin merely gave hints to brother philosophers and left them to run the hints down. For instance, he suggested to M. De Saussure, of Geneva, who succeeded in ascending Mont Blanc, the idea of ascertaining the lateral attraction of the Jura Mountains for the purpose of discovering the mean density of the earth upon the Newtonian theory of gravitation. This was subsequently done with complete success by Nevil Maskelyne on Mt. Schehallion in Perthshire. To Ingenhousz he suggested the idea of "hanging a weight on a spiral spring, to discover if bodies gravitated differently to the earth during the conjunctions of the sun and moon, compared with other times."

He gave very close study to the philosophy of waterspouts and whirlwinds and came to the conclusion that they were generated by the same causes, and were of the same nature, "the only Difference between them being, that the one passes over Land, the other over Water." He was the first person to discover that northeast storms did not begin in the northeast at all. The manner in which he did it is another good illustration of his quickness in noting the significance of every fact by which his attention was challenged. He desired to observe a lunar eclipse at nine o'clock in the evening at Philadelphia, but his efforts were frustrated by a northeast storm, which lasted for a night and a day, and did much damage all along the Atlantic coast. To his surprise he afterwards learnt from the Boston newspapers that the eclipse had been visible there, and, upon writing to his brother for particulars, was informed by him that it had been over for an hour when the storm set in at Boston; though it was apparently fair to assume that the storm began sooner at Boston than at Philadelphia. This information and further inquiry satisfied him that northeast storms commence southward and work their way to the northeast at the rate of a hundred miles an hour. When we read the words in which he stated his theory of such storms, we begin to understand what Sir Humphry Davy meant in saying that science appeared in Franklin's language in a dress wonderfully decorous, and best adapted to display her native loveliness.

Suppose [he said to Jared Eliot] a great tract of
country, land and sea, to wit, Florida and the Bay of
Mexico, to have clear weather for several days, and to
be heated by the sun, and its air thereby exceedingly
rarefied. Suppose the country northeastward, as
Pennsylvania, New England, Nova Scotia, and
Newfoundland, to be at the same time covered with
clouds, and its air chilled and condensed. The rarefied
air being lighter must rise, and the denser air next to
it will press into its place; that will be followed by
the next denser air, that by the next, and so on. Thus,
when I have a fire in my chimney, there is a current of
air constantly flowing from the door to the chimney;
but the beginning of the motion was at the chimney,
where the air being rarefied by the fire rising, its
place was supplied by the cooler air that was next to
it, and the place of that by the next, and so on to the
door. So the water in a long sluice or mill-race, being
stopped by a gate, is at rest like the air in a calm;
but as soon as you open the gate at one end to let it
out, the water next the gate begins first to move, that
which is next to it follows; and so, though the water
proceeds forward to the gate, the motion which began
there runs backward, if one may so speak, to the upper
end of the race, where the water is last in motion.

It may be truly said of every province of scientific research into which Franklin ventured that he brought to it a bold and original spirit of speculation which gave it new interest and meaning. Even when he was not the first to kindle a light, he had a happy and effective way of trimming it anew and freshening its radiance. To Collinson he wrote on one occasion, "But I must own I am much in the _Dark_ about _Light_." But noonday is not more luminous than what he had to say on the subject in this letter.

May not all the Phaenomena of Light [he asked] be more
conveniently solved, by supposing universal Space
filled with a subtle elastic Fluid, which, when at
rest, is not visible, but whose Vibrations affect that
fine Sense the Eye, as those of Air do the grosser
Organs of the Ear? We do not, in the Case of Sound,
imagine that any sonorous Particles are thrown off from
a Bell, for Instance, and fly in strait Lines to the
Ear; why must we believe that luminous Particles leave
the Sun and proceed to the Eye? Some Diamonds, if
rubbed, shine in the Dark, without losing any Part of
their Matter. I can make an Electrical Spark as big as
the Flame of a Candle, much brighter, and, therefore,
visible farther, yet this is without Fuel; and, I am
persuaded no part of the Electric Fluid flies off in
such Case to distant Places, but all goes directly, and
is to be found in the Place to which I destine it. May
not different Degrees of Vibration of the
above-mentioned Universal Medium occasion the
Appearances of different Colours? I think the Electric
Fluid is always the same; yet I find that weaker and
stronger Sparks differ in apparent Colour; some white,
blue, purple, red; the strongest, White; weak ones,
red. Thus different Degrees of Vibration given to the
Air produce the 7 different Sounds in Music, analagous
to the 7 Colours, yet the Medium, Air, is the same.

"Universal Space, as far as we know of it," he declared in his _Loose Thoughts on a Universal Fluid_, "seems to be filled with a subtil Fluid, whose Motion, or Vibration is called Light." And he then proceeds to found on this statement a series of speculations marked by too high a degree of temerity to have much scientific value. One sentiment in the paper, however, is well worth recalling as showing how clearly its author had grasped the conservation of matter. "The Power of Man relative to Matter," he observed, "seems limited to the dividing it, or mixing the various kinds of it, or changing its Form and Appearance by different Compositions of it; but does not extend to the making or creating of new Matter, or annihilating the old."

The Science of Palaeontology was in its infancy during the lifetime of Franklin. Many years before Cuvier gave the name of mastodon to the prehistoric beast, whose fossil remains had been brought to sight from time to time in different parts of the world, George Croghan, the Indian trader, sent to Franklin a box of tusks and grinders, which had been found near the Ohio, and which he supposed to be parts of a dismembered elephant. In his reply of thanks, Franklin observed that the tusks were nearly of the same form and texture as those of the African and Asiatic elephant. "But the grinders differ," he added, "being full of knobs, like the grinders of a carnivorous animal; when those of the elephant, who eats only vegetables, are almost smooth. But then we know of no other animal with tusks like an elephant, to whom such grinders might belong." The fact that, while elephants inhabited hot countries only, fragments such as those sent to him by Croghan were found in climates like those of the Ohio Territory and Siberia, looked, Franklin concluded, "as if the earth had anciently been in another position, and the climates differently placed from what they are at present." Contrasting the observations of this letter with the paper read long afterwards by Thomas Jefferson before the American Philosophical Society on the bones of a large prehistoric quadruped resembling the sloth, William B. Scott, the American palaeontologist, remarks:

Franklin's opinions are nearer to our present beliefs
than were Jefferson's, written nearly forty years
later. Of course, we now know that Franklin was
mistaken in supposing that such bones were found only
in what is now Kentucky and in Peru, and his comparison
of the teeth of the mastodon with the "grinders of a
carnivorous animal" is not very happy, but the
inferences are remarkably sound, when we consider the
state of geological knowledge in 1767.

In a letter to Antoine Court de Gebelin, the author of the _Monde Primitif_, Franklin gave him a valuable caution, in relation to apparent linguistic variations. Strangers, who learnt the language of an Indian nation, he said, finding no orthography, formed each his own orthography according to the usual sounds given to the letters in his own language. Thus the same words of the Mohawk language, written by an English, a French and a German interpreter, often differed very much in the spelling.

Franklin's letters to Herschel, Maskelyne, Rittenhouse, Humphrey Marshall and James Bowdoin reveal a keen interest in astronomy, but this is not one of the fields from which he came off _cum laude_. Gratifying to the pride of an American, however, is an observation which he made to William Herschel, when the latter sent to him for the American Philosophical Society a catalogue of one thousand new nebulae and star-clusters and stated at the same time that he had discovered two satellites, which revolved about the Georgian planet. In congratulating him on the discovery, Franklin said:

You have wonderfully extended the Power of human
Vision, and are daily making us Acquainted with Regions
of the Universe totally unknown to mankind in former
Ages. Had Fortune plac'd you in this part of America,
your Progress in these Discoveries might have been
still more rapid, as from the more frequent clearness
of our Air, we have near one Third more in the year of
good observing Days than there are in England.

The production of cold by evaporation was another subject which enlisted the eager interest of Franklin. In co-operation with Dr. Hadley, the Professor of Chemistry at Cambridge, England, he was so successful in covering a ball with ice by wetting it from time to time with ether, and blowing upon the ether with a bellows, that he could write to John Lining in these words: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day, if he were to stand in a passage through which the wind blew briskly, and to be wet frequently with ether, a spirit that is more inflammable than brandy, or common spirits of wine."

Geology was in its infancy during Franklin's time, but he hazarded some conjectures about the formation of the earth that are perhaps not less trustworthy than those advanced by riper geologists. In the letter, in which these conjectures were communicated to the Abbe Soulavie, he said:

Part of the high county of Derby being probably as much
above the level of the sea, as the coal mines of
Whitehaven were below it, seemed a proof that there had
been a great _bouleversement_ in the surface of that
Island (Great Britain), some part of it having been
depressed under the sea, and other parts which had been
under it being raised above it.... Such changes in the
superficial parts of the globe [he continued] seemed to
me unlikely to happen if the earth were solid to the
centre. I therefore imagined that the internal parts
might be a fluid more dense, and of greater specific
gravity than any of the solids we are acquainted with;
which therefore might swim in or upon that fluid. Thus
the surface of the globe would be a shell, capable of
being broken and disordered by the violent movements of
the fluid on which it rested.

The letter contains other speculations equally bold:

It has long been a supposition of mine that the iron
contained in the substance of this globe, has made it
capable of becoming as it is a great magnet. That the
fluid of magnetism exists perhaps in all space; so that
there is a magnetical North and South of the universe
as well as of this globe, and that if it were possible
for a man to fly from star to star, he might govern his
course by the compass. That it was by the power of this
general magnetism this globe became a particular
magnet. In soft or hot iron the fluid of magnetism is
naturally diffused equally; when within the influence
of the magnet, it is drawn to one end of the Iron, made
denser there, and rare at the other, while the iron
continues soft and hot, it is only a temporary magnet:
If it cools or grows hard in that situation, it becomes
a permanent one, the magnetic fluid not easily resuming
its equilibrium. Perhaps it may be owing to the
permanent magnetism of this globe, which it had not at
first, that its axis is at present kept parallel to
itself, and not liable to the changes it formerly
suffered, which occasioned the rupture of its shell,
the submersions and emersions of its lands and the
confusion of its seasons.

It was probably, Franklin thought, different relations between the earth and its axis in the past that caused much of Europe, including the mountains of Passy, on which he lived, and which were composed of limestone rock and sea shells, to be abandoned by the sea, and to change its ancient climate, which seemed, he said, to have been a hot one.

The physical convulsions to which the earth had been subject in the past were, however, in his opinion beneficent.

Had [he said in a letter to Sir John Pringle] the
different strata of clay, gravel, marble, coals,
limestone, sand, minerals, &c., continued to lie level,
one under the other, as they may be supposed to have
done before these convulsions, we should have had the
use only of a few of the uppermost of the strata, the
others lying too deep and too difficult to be come at;
but the shell of the earth being broke, and the
fragments thrown into this oblique position, the
disjointed ends of a great number of strata of
different kinds are brought up to-day, and a great
variety of useful materials put into our power, which
would otherwise have remained eternally concealed from
us. So that what has been usually looked upon as a
_ruin_ suffered by this part of the universe, was, in
reality, only a preparation or means of rendering the
earth more fit for use, more capable of being to
mankind a convenient and comfortable habitation.

The scientific conjectures of Franklin may not always have been sound, but they are invariably so readable that we experience no difficulty in understanding why the Abbe Raynal should have preferred his fictions to other men's truths.

FOOTNOTES:

[51] The lightning rod in its origin encountered the same religious misgivings as inoculation and insurance and many other ideas which have promoted human progress and happiness. The Rev. Thomas Prince at the time of the Lisbon earthquake thought that the more lightning rods there were the greater was the danger that the earth might become perilously surcharged with electricity. "In Boston," he said, "are more erected than anywhere else in New England; and Boston seems to be more dreadfully shaken. Oh! there is no getting out of the Mighty Hand of God! If we think to avoid it in the Air we can not in the Earth. Yea, it may grow more fatal."

[52] The lines under the portrait of Franklin by Cochin do not hesitate to exalt him above the most powerful forces of Nature and the authority of the Gods:

"C'est l'honneur et l'appui du nouvel hemisphere,
Les flots de l'Ocean s'abaissent a sa voix;
Il reprime ou dirige a son gre le tonnerre.
Qui desarme les dieux peut-il craindre les rois?"

[53] "With Franklin grasp the lightning's fiery wing," is a line in Thomas Campbell's _Pleasures of Hope_. In his _Age of Bronze_, Byron asks in one place why the Atlantic should "gird a tyrant's grave"

"While Franklin's quiet memory climbs to heaven,
Calming the lightning which he thence hath riven."

And in another place in the same poem he speaks of

"Stoic Franklin's energetic shade,
Robed in the lightnings which his hand allayed."

Crabbe in his tribute to "Divine Philosophy" in the _Library_ exclaims,

"'Tis hers the lightning from the clouds to call,
And teach the fiery mischief where to fall."

[54] The inductive process by which Franklin arrived at the identity of lightning and electricity was set forth in one of his letters to John Lining, of Charleston, dated March 18, 1755. The minutes kept by him of his experiments and observations, contained, he said, the following entry:

"November 7, 1749. Electrical fluid agrees with lightning in these particulars. 1. Giving light. 2. Colour of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell. The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the Experiment be made."

[55] The standing of Franklin as an inventor would be better established if he had not been so resolute in his unwillingness to take out patents upon his inventions. Besides the various inventions mentioned by us in the text, he was the father of other valuable mechanical conceptions. The first hint of the art of engraving upon earthenware appears to have originated with him. Moved by his constant desire to inculcate moral truths, he suggested about 1753 to a correspondent the idea of engraving from copper plates on square chimney tiles "moral prints"; "which," to use his words, "being about our Chimneys, and constantly in the Eyes of Children when by the Fireside, might give Parents an Opportunity, in explaining them, to impress moral Sentiments."

He also appears to have anticipated the Argand burner. A description has come down to us of a lamp devised by him which, with only three small wicks, had a lustre equal to six candles. It was fitted with a pipe that supplied fresh and cool air to its lights. If Franklin did not invent, he was the first to communicate to his friend, Mr. Viny, the wheel manufacturer at Tenderden, Kent, the art of flexing timber used in making wheels for vehicles. But of few things did Franklin take a gloomier view than the fate of the inventor as his observations in a letter to John Lining, dated March 18, 1755, demonstrate. "One would not," he said, "of all faculties or qualities of the mind, wish, for a friend, or a child, that he should have that of invention. For his attempts to benefit mankind in that way, however well imagined, if they do not succeed, expose him, though very unjustly, to general ridicule and contempt; and, if they do succeed, to envy, robbery, and abuse."