Chapter XIV: TECHNOLOGY.--Employment of Acetic or Formic Acid in (2)

The stump puller shown in the accompanying engraving (page 130) is exceedingly powerful, as, by a system of compound levers, a pull of one pound on the operating bar will exert a pull of 384 pounds on the stump, and if the lifting chain be passed around a single pulley, this power is doubled. With one of these machines one man has pulled a green maple stump two feet in diameter from clay soil. The pulling mechanism is supported by a tripod, to the upper end of which is secured a chain carrying a bar or plate provided with a bearing in which slides a notched bar. Meshing with the notches of this bar are the teeth of a pawl, which is so connected, by levers, with the operating handle that the downward movement of the latter will raise the pawl and notched bar and the chain attached to its lower end. A sliding bolt then holds the notched bar in its raised position, when the handle can be raised to enable the pawl to engage with the next lower teeth of the bar. Thus, by a succession of up and down movements of the handle, the notched bar may be elevated its entire length, or until the stump is pulled completely out. It will be seen that the sliding bolt permits of the upward, but prevents the downward, movement of the notched bar when the pawl is disengaged and slides downward. But, by means of a suitably arranged hand lever, the pawl may be moved so as to be out of contact with the bar, and, at the same time, the bolt, which is pressed forward by a spring, may be moved to disengage it from the notch in the bar, which may then be adjusted in any desired position. The machine is built of steel and malleable iron.

This invention has been patented by Messrs. R. R. Tichenor and P. Walker, of Henning, Minn.

The Defense of New York within Thirty Days' Time.

The idea seems to prevail that the United States is absolutely helpless against a naval attack from England. I think this idea is entirely erroneous. There is the pneumatic gun, capable now of throwing 300 lb. of nitro-glycerine, which amount could easily be increased to 1,000 lb. For the value of one modern ironclad, 150 steamers with such a gun could be put in service in two weeks by the United States, because any steamer of 100 feet or over would answer; while the gun, being a mere tube, subjected to but 1,000 lb. of air per square inch, with air-compressing machinery, is all so available and quickly built that a month would put the United States into possession of 500 of them. If, now, 20 such steamers be told off for each ironclad sent against us, even if two-thirds were sunk, they would, before being entirely demolished, succeed in depositing 5 to 10 tons of nitro-glycerine on the deck of the ironclad, and exploding it.

Would not the effect of repeated explosions of 1,000 lb. of nitro-glycerine blow the deck in, dismount the guns and engine, and shake the armor loose, as the explosions of the Monitors' guns did when they were in service in the late war--the heads of bolts and other fastenings of the armor flying off from the concussion.

Then there is the submarine boat, that has already stayed under water thirty minutes with its crew, and been easily and correctly guided. What is in the way of using ten such boats to each ironclad, one of which would unquestionably succeed in placing 1,000 lb. of nitro-glycerine under the ironclad, the explosion of which would be heard from? Because the explosion of 90 lb. of gun-cotton did not materially damage an ironclad, can it be reasoned that 1,000 lb. of nitro-glycerine, which would have twenty-five times the force of 90 lb. of gun-cotton, would be equally ineffective? Hardly, I think.

Nets, etc., would not prevent such boats from diving under them, while they would only impede the speed and maneuvering of the ironclad, and render her more easily approached.

Blucher, the German cavalry officer, insisted that it was the impression and belief existing in Germany that Napoleon was invincible, and the Germans helpless, that alone prevented them from conquering. When the occasion came when he could demonstrate this, the Germans and allies easily defeated and dethroned Napoleon.

It is similarly true in this country, for too many believe that the English ironclad is invincible, and this impression makes cowards of too many. Give the nitro-glycerine gun and submarine boat a trial, if occasion arises, and England's ironclads will succumb as easily as Napoleon when sufficient power of the right kind was brought to bear on him. The right kind of power to apply to England is nitro-glycerine and dynamite, which could be ready with guns and boats in a month or less. One hundred days sufficed to build the first Monitor many years ago, and much less time will be needed for dynamite guns.

WAYNE.

Electroplating with Platinum.

Platinum has not been much used in electroplating, notwithstanding its hard, durable, and protective properties. This is, perhaps, chiefly owing to the practical difficulty of obtaining a good firm "reguline" deposit. A process for effecting this has, however, been brought out recently by a Mr. Bright, whose patents have been acquired by the Bright Platinum Plating Company, and are in actual operation in London at works established there. Platinum has the advantage of keeping its color where silver, brass, or copper becomes discolored, and will, to some extent at least, replace the use of these metals in electrotyping. It will be highly useful in plating chemists' crucibles and so on. German silver, for example, plated with platinum can be used to manipulate strong acids. By the Bright process, platinum can be deposited on any surface which can be electroplated with other metals.

COMBINED BRUSH AND COMB CLEANER.

The invention herewith illustrated relates to a device for cleaning brushes and combs. It consists of a handle or body of suitable form, provided at one end with a brush, and at the opposite end with thin curved fingers of metal, or equivalent elastic material, adapted to enter between the teeth of the comb or the bristles of the brush. In making use of the device the hooks are employed to loosen and remove, as far as possible, the hairs or other foreign matter, after which the brush is employed to complete the operation. It is intended to afford a cheap, simple, and efficient means of cleaning articles in daily use in every household, and is virtually sure, considering the low cost at which it can be manufactured, to become a staple article of merchandise. The invention has been patented by Mr. J. O. Brookbank, of Driftwood, Cameron County, Pa., to whom all particulars relating to purchase of rights for the United States and Canada should be addressed.

Correspondence.

Coincidence of Charleston Earthquake with a Reported Eruption in the Tonga Group.

_To the Editor of the Scientific American:_

I would like to call your attention to a reported coincidence, described in a letter in the London _Times_ of December last. An interview with captain and crew of a vessel just then arrived at Sydney, Australia, from Tonga Islands, is given. The captain is represented assaying that while lying off the islands on the night of the 31st of August, 1886, he observed a most terrific eruption of a volcano situated on one of them, accompanied by earthquake shocks, and the vessel received showers of dust and ashes. The occurrence on the same night with the Charleston earthquake on this continent is curious, to say the least. The statement might be acceptable to those of your readers interested in seismic disturbances.

P. MAX. FOSHAY.

Beaver Falls, Pa., February 2, 1887.

Incendiary Birds.

_To the Editor of the Scientific American:_

I write to relate an incident which may be of interest to some of the readers of your valuable paper. There is a bar iron mill, situated in a neighboring town four miles from here, that has been on fire three or four times, in which the English sparrow might be called the incendiary. These sparrows pick up old pieces of cotton waste, which they build in their nests, among the timbers of the roof of the mill, and in every case of the fires above mentioned, these nests were the cause, either from spontaneous combustion or from sparks from the hot iron striking and lodging in the nest. If you could suggest some way of getting rid of the sparrows, I think the manager of the mill would be glad to adopt your plan.

R. W. KEAR.

Pottsville, Pa., February 14, 1887.

Charcoal as Fossil.

_To the Editor of the Scientific American:_

Perhaps charcoal has not often been observed as occurring naturally with mineral coal, though, as a result of metamorphism, graphite is not uncommon in coal districts.

In a variety of bituminous coal that comes from Tennessee, and that is largely used in this State, there are to be seen along in the cleavage planes films of true charcoal, in varying quantity, but commonly thin. This coal has been coming to us for several years, and all the while I have noticed in it the presence of the charcoal. I have scarcely ever put coal into the fire without making the observation; and there is perhaps not a lump, of size at all considerable, that does not contain these films.

On close examination, I have frequently found that the surface of the films on the broken lumps contains a delicate tracery, closely resembling vegetable impressions. The tracery is not so well marked as a fossil imprint, but not so indistinct as to escape notice.

J. F. B.

Emory College, Ga.

Phosphorescent Birds.

_To the Editor of the Scientific American:_

In reading of the habits of the wading birds, and particularly of the crane, I do not find that naturalists give any account of their manner of attracting their prey at night. My attention was called to the matter while gigging for fish, by frequently observing dim phosphoric lights appear and disappear along the shore like jack o' lanterns, which I for a long time supposed them to be. Oh one occasion I fired at such a light, and brought down a large blue crane, on which the phosphoric spots were clearly visible after death. There are two such spots; the larger being high up on the breast and the smaller at the bottom of the breast bone, the bird having power to reveal and conceal them at will. I have since stuffed many of the water walkers, and find that all have the same general arrangement of the feathers, and, as I believe, the same power of lighting up the water to attract the fish. Will some naturalist who is posted on this subject please throw some further light upon it, for the benefit of science?

ISAAC N. WORRALL.

Topeka, Kansas.

Canned Fish, Meats, etc.

A correspondent in British Columbia, who is engaged in the business, gives us the following practical information:

Noticing your reply to a correspondent anent canned goods, I recently opened several cans of salmon that were processed in July of 1879, 1880, 1881, and on comparing them with last season's cans, found it impossible to detect the slightest difference. I hold that if a can is once perfectly sealed, the contents will remain unaltered as long as the metal casing remains intact.

A can will keep if every portion of the contents has been subjected to a temperature of 212° Fah., whether the air is expelled or not, as my experiments have conclusively proved.

When I first began the business, I was taught that the air unless expelled would cause the contents to deteriorate, and that was the reason the cans were vented. I soon found it was a mistake. The venting is done for the purpose of testing for leaks. A tight can has a sound that cannot be mistaken for a leaky one. If your correspondent boils his fish, flesh, or fowl with the vents open, he will have dry cans for his pains. The vents must be closed when cooking, and opened, in the case of meats, after boiling one hour, then closed and returned to kettle, and boil three hours for fish and less for meat without bone. Fruit is vented and closed when finished.

S. H.

OUR WINTER BIRDS.

BY E. M. HASBROUCK.

It is a popular belief that the woods and fields in winter time are void of bird life, and are what they appear at a distance--a cold, bleak, and desolate waste.

This opinion, however, is not correct. It is true that the birds, which were so numerous during the summer, have left us and gone to their winter homes, but as they departed an entirely different fauna started from a colder climate, and gradually took their place. I refer to the birds of the northern part of Canada and the fur countries, whose summer homes are in these desolate regions, and which on the approach of winter are driven southward, making a temporary stay with us until the rigors of an Arctic winter shall have departed, and once more left their homes in an inhabitable condition.

A glance at these birds will take one into the same localities that have been so often traversed in the summer time, and once within the woods, the fact that they are cold and leafless is lost sight of. One can now find birds entirely different from any that he has heretofore seen, and at the same time learn several facts of interest concerning birds with which he considers himself well acquainted; as, for instance, the American goldfinch, which is supposed to migrate in the fall, will be found in the swampy woods in large flocks, but with plumage so changed that they will probably not be recognized, being of a somber brown color, and sexes undistinguishable. Why hundreds of a species, the majority of which migrate regularly, and which do not reach us until late in the spring, should change their dress and remain with us throughout our most severe winters is a problem.

In company with them will often be found the pine linnet and common red poll. These little finches are rather rare, and are seldom found together in any great numbers. They leave the North in large flocks, but as they journey southward break up into smaller and smaller companies, until only a few are left together. These join interests with the nearest goldfinches, and remain with them throughout the winter.

The results of a visit to the fields, on some clear day, will often repay a somewhat wearisome tramp. The snow buntings and shore larks frequent such places in large numbers, and a locality where the ground has been swept bare of snow, or is covered with a growth of weeds, is a favorite feeding ground.

Their food consists entirely of the seeds, and a spot once chosen by them is seldom forsaken until all in this line has been eaten.

The buntings will be found in flocks of from a dozen to two hundred, and in some even more. Their appearance when flying is pure white, but the upper parts of a specimen in the hand will be found mostly black. They are extremely shy, and when approached spring into the air and dart away in a manner that would indicate their intention of departing for the next county; but should you return that way in the course of half an hour, you will, in all probability, find them in the same place.

The shore larks, although feeding on the same grounds, seldom mix with the buntings, preferring to keep in flocks by themselves, and are worthy of attention, inasmuch as they have one marked peculiarity; this is the small tuft of feathers on each side of the head, resembling minute horns, which are raised and lowered at pleasure. (See cut.)

The majority of these birds reach us at the approach of cold weather, although a few spend the summer here and rear their young. They are less timid than the snow bunting, and may often be approached quite close.

These two species form about all the attraction to be found to any extent in the fields, and, aside from an occasional hawk, only one more species frequents them, a species that is worth going miles to see--the snowy owl.

These birds reach us about the last of November and remain until the last of February, frequenting the neighborhood of some body of water, and seldom straying from it more than a mile or two. To see them and become at all acquainted with their habits, one must face all kinds of weather, possess untiring energy, and must undergo a considerable amount of fatigue. He will find them in the open country (as they frequent such ground altogether, seldom, if ever, entering the woods), perched on some fence post or stump, where, if undisturbed, they will remain for a considerable length of time, intently watching for mice, of which their food largely consists, set off by an occasional rabbit. They are extremely rare. One may tramp the fields for several days without success, and then again find one the first hour out.

On December 20, 1886, the writer started on a trip to Oneida Lake, N. Y., intending to devote his attention entirely to these birds; was gone four days, and saw five birds. This, of course, was exceptional, but shows what may happen.

In the dense pine and hemlock swamps several other species of owls are found, which are much more numerous at this season than in the summer. These are the long eared and short eared owls, with an occasional barred owl; but the most interesting of all is the Acadian or saw-whet, one of the smallest of the family and little known. It is far from common, being met with only at intervals. Its note, which closely resembles the filing of a large saw, occasionally betrays it; while at the same time it has a tendency to stray into barns and out-buildings, thus affording an opportunity for capture.

As it is not generally known, a description may be of some benefit. "Upper parts, including wings and tail, uniform chocolate-brown, spotted with white; under parts white, thickly streaked lengthwise with the color of the back; face, white."

In general appearance, they are the same as all owls, but when seen in the woods have a somewhat comical appearance, owing to their wise look for so small a bird.

We have often heard of the shrikes, or butcher birds, that capture small birds and impale them on the thorns of bushes. Many of us have wished to see them, and wondered where and when they were to be found. Now is the time. Any clump of bushes or young second-growth is a likely place to find them, for there are two species which visit us every winter and frequent these places. These are the great northern and loggerhead shrikes, the latter being most common; both bear a general resemblance, but differ mainly in size and in markings on the under parts. One can find them almost any day, perched on the topmost branch of some tree or bush, steadily eyeing the surrounding bushes in search of some victim, while on a thornbush near by will be found numberless moles, mice, and an occasional bird, awaiting the appetite of the marauder.

Aside from the goldfinches, many other birds of different species, instead of migrating with the rest, remain behind, and are to be found, on almost any pleasant day, in the warmer and more secluded parts of the swamp. Among these are the robin, golden-winged, downy, and hairy woodpeckers, the white-bellied nuthatch, and chickadees. These last are, perhaps, the most numerous of all our winter birds; whole flocks roam from one end of the swamp to the other, and I think there is no pleasanter sound to be heard in the woods in winter than to hear their clear "chick-a-dee-de-de-de" from a score of little throats, or to see them clinging to the branches and acting as familiarly as though no one was within sight or hearing. An occasional meadow lark will be flushed from the tall grass in some sheltered spot, while on the open streams will be found black ducks and mallards, whistlers and mergansers of two species, the hooded and buff-breasted or common sheldrake.

Truly, then, with all this material awaiting us, the fields and forests will be found inviting, and you who have never traversed them in winter do so now, and get a new interest awakened in them.

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IT is not long since we spoke of the benefits conferred on the farmer by the inventor. The following statement is a good illustration of our views as then presented. It is taken from our contemporary, the _New England Farmer_. "By the use of mowing machines and horse rakes and a horse hay fork, two boys in Connecticut last summer cut, raked, and helped to stow away 100 tons of hay, while their father was disabled from work by illness. Under such conditions a farmer is apt to feel like blessing the man who invents labor-saving machinery."

THERMOSCOPIC BALANCE.

BY GEO. M. HOPKINS.

The action of this instrument is due to the facility with which liquids evaporate in a vacuum. A small amount of heat is sufficient to vaporize the liquid to the extent required to secure the desired action. The instrument is provided with a glass tube bent twice at right angles, and having a bulb blown on each end. The tube and the bulbs are partly filled with water, and a vacuum is secured by boiling the water in the bulbs before sealing them. The center of the tube is furnished with V-pivots, which rest in bearings in the top of the forked column. The column also supports a metal screen, which is bright one side and black on the other. Two pins project from the shield, to limit the movements of the glass tube and bulbs.

When the instrument is in use, the screen is placed toward the source of heat, and when radiant heat strikes the bulb which is unshielded by the screen, the water in that bulb is vaporized, and sufficient pressure is produced to drive the water upward into the bulb behind the screen. When a little more than half of the water has been in this manner forced from the lower to the higher bulb, the upper bulb preponderates. The tube and bulbs are supported on their pivot so as to secure unstable equilibrium, so that, when the upper bulb begins to descend, it completes its excursion at once, and exposes the full bulb to the radiant heat, at the same time carrying its empty bulb behind the screen, where it cools. The transfer of the water from the full bulb to the empty one now occurs as before. This operation is repeated so long as the bulbs are exposed to the action of radiant heat. The oscillations may be quickened by smoking the sides of the bulbs remote from the screen, and still greater rapidity of action may be secured by concentrating the heat on the bulbs by means of condensers or reflectors.

The Duration of the Sun.

The _Builders' Weekly Reporter_ (London) has an interesting account of a lecture at the Royal Institute, given by Professor Sir William Thomson, on the latest dynamical theories regarding the "probable origin, total amount, and possible duration of the sun's heat." During the short 3,000 years or more of which man possesses historic records there was, the learned physicist showed, no trace of variation in solar energy; and there was no distinct evidence of it even though the earth, as a whole, from being nearer the sun, received in January 6½ per cent more heat than in July. But in the millions of years which geology carried us back, it might safely be said there must have been great changes. How had the solar fires been maintained during those ages? The scientific answer to this question was the theory of Helmholtz that the sun was a vast globe gradually cooling, but as it cooled, shrinking, and that the shrinkage--which was the effect of gravity upon its mass--kept up its temperature. The total of the sun's heat was equal to that which would be required to keep up 476,000 millions of millions of millions horse power, or about 78,000 horse power for every square meter--a little more than a square yard--and yet the modern dynamical theory of heat shows that the sun's mass would require only to fall in or contract thirty-five meters per annum to keep up that tremendous energy. At this rate, the solar radius in 2,000 years' time would be about one hundredth per cent less than at present. A time would come when the temperature would fall, and it was thus inconceivable that the sun would continue to emit heat sufficient to sustain existing life on the globe for more than 10,000,000 years. Applying the same principles retrospectively, they could not suppose that the sun had existed for more than twenty million years, no matter what might have been its origin--whether it came into existence from the clash of worlds pre-existing, or of diffused nebulous matter. There was a great clinging by geologists and biologists to vastly longer periods, but the physicist, treating it as a dynamic question with calculable elements, could come to no other conclusion materially different from what he had stated. Sir William Thomson declined to discuss any chemical source of heat, which, whatever its effect when primeval elements first came into contact, was absolutely insignificant compared with the effects of gravity after globes like the sun and the earth had been formed. In all these speculations they were in the end driven to the ultimate elements of matter, to the question--when they thought what became of all the sun's heat--what is the luminiferous ether that fills space, and to that most wonderful form of force upon which Faraday spent so much of the thought of his later years--gravity. The lecture was heard with deep interest and close attention.

IMPROVED MARINE DREDGER.

The twin screw dredger Dolphin was recently constructed for the Colonies, under the direction of Sir John Coode, assisted by Mr. Wm. Matthews, C.E., and is especially designed, says the _Engineer_, for harbor improvements in the West Indies. The dimensions are:

Ft. In.
Length between perpendiculars 130 0
Breadth moulded 30 0
Depth 8 0
ENGINES--Compound surface condensing, I.H.P 250
Stroke of pumps 14
Diameter of high pressure cylinder 16½
" low pressure " 33
Length of stroke 24
Diameter of air pump 11½
" circulating pump 6½
" feed pumps 2½
" bilge pumps 2½

The boiler is of steel, for a working pressure of 90 lb. per square inch. The bucket ladder works through a well formed in the center of the vessel, and dredges to a depth of 33 ft. below the water level, and the buckets are made wholly of steel, and are capable of lifting 250 tons of free soil per hour. Triple-geared winches are supplied at bow and stern for working the mooring chains, the barrels of which can be worked independently or conjointly, as required. The cabins for the officers and crew are of the most complete description; those of the former being fitted on starboard side of the well, and consist of rooms for the captain, mate, and engineers, also mess room. All the rooms are large and efficiently lighted and ventilated. A powerful crane is erected at forward end for overhauling the buckets, hoisting gear, etc.

Hydraulic Dredging at Washington.

At a recent meeting of the Engineers' Club of Philadelphia, a paper by Conway B. Hunt was read on hydraulic dredging machinery.

The paper mentions the early application of the principle of hydraulic dredging, that is, the mixing of dredged material with water and then removing the mixture by suction or otherwise; and after referring briefly to the Roy Stone and Bowers dredges as typical machines, describes in detail the Von Schmidt dredge. Two of these dredges are engaged on the improvement of the Potomac River at Washington, D. C., under the United States Government. Each is 100 feet by 50 feet, with a semicircular bow, around which travels a vertical suction pipe, 22 in. in diameter, and telescopic. At its foot is a conical hood, beneath which works a rotary excavating plow, 8 feet in diameter. The suction is produced by a powerful centrifugal pump, run by a 200 horse power engine.

The discharge pipe is 20 in. in diameter, has rubber hose joint connections, and is carried to the shore on pontoons. The material was mixed with from three to ten times its volume of water, and discharged at distances up to 3,500 feet from the dredge, and at from 6 to 10 feet above water. A year's record shows an average of 175 cubic yards per working hour, and 2,300 yards per day, for each dredge. The work was done, by contract, at prices of 12.37 cts., 15 cts., and 15.45 cts. per cubic yard, which includes the cost of levees to confine the semi fluid material, drains to carry off the water, etc. The final estimates were specified to be taken by cross sections of the completed fill after it had become solidified and compacted. In conclusion, it is noted that the devices and details of hydraulic dredging machines are the subjects of numerous patents, and their most efficient combination may be long deferred. The large number of machines that are still in the experimental stage of development would indicate that the best results attainable from this class of dredges have not yet been accomplished.

A New Sugar Process.

The details of the process vary with quality of beets. To a vat containing the secondary products to be treated are added calculated quantities of diluted hydrochloric acid and milk of lime at 25° B. The mass is heated to the boiling point by a steam coil. In a separate vat the product is diluted with water at 75° C. to 23° B., and subsequently run through Puvrez filtering bags. The filtrate is clear in color, and is received in a measuring tank, from which it is run into the diffusion battery. In the latter but few changes are necessary. It is said that by this method an additional 1 per cent sugar is extracted from the beet, and the white sugar obtained can be at once placed upon the market.

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THERE were exported last season from Prince Edward Island 91,000 cases of lobsters.

THE NORTHERN LIGHTS.

When, in 1752, Franklin succeeded, through a kite sent up into a storm cloud, in obtaining an electric spark at the extremity of the cord, which had been made a conductor through the rain, it was no longer possible to doubt that lightning was but an immense electric discharge between two clouds, or a discharge between a cloud and the earth. This discovery was of great importance, since it connected with the laws of physics certain phenomena which, until then, had passed for marvelous, and in which nothing but supernatural and mysterious manifestations were seen.

The aurora borealis, which is more difficult to understand, and which necessitates more extended scientific notions, has remained much longer unexplained. This enigmatic phenomenon was especially striking to the imagination of ancient peoples. It was regarded as an omen of inauspicious events, and the historians who describe it affirm that, at times, armies have been seen passing through the bloody heavens, and that the clash of arms has been heard.

It is now known that the aurora borealis has the same origin as lightning, that it is one of the visible manifestations of atmospheric electricity, and that it is due to slow movements of that fluid, while lightning is the result of violent motions. The effects of the aurora and of the thunderbolt are absolutely different; but between them there is an intermediary that connects them, and this is heat lightning.

These elementary notions are now the property of science; but the study of the aurora has hitherto been only partially outlined. Travelers and physicists have, indeed, given numerous descriptions, but it has remained to find the bonds that unite these so important phenomena in the economy of the globe, to study the causes that set them in action, to observe the correlations that they may offer, and to discuss theories. This is a labor that Mr. S. Lemstrom has been engaged in for several years, and we now propose to analyze the results published by this great Finnish physicist.

The author of this important work, who has long been occupied in the study of the aurora borealis, so frequent in his country, was attached to the polar expedition made in 1868 by Nordenskjold. He was led to begin a series of important observations. In 1871 he visited Finnish Lapland, and, after a series of ingenious researches, constructed an apparatus that permitted him to artificially reproduce the light of the aurora, and to present science with a summary of new and incontestable facts.

Mr. Lemstrom has observed a large number of auroræ, and before touching upon theoretic questions, we shall give his description of one of the phenomena that seems to him to be the completest. On the 18th of October, 1868, the steamer Sophia was nearing the coast of Norway, after battling with a furious sea for three days in succession.

"To the west of the horizon we remarked two strata of clouds that were clearly separated by a blue band of the heavens, crossed by a band striated with a pale yellow. It was the feeble beginning of an aurora, whose splendor was soon to surpass all the phenomena of the same kind that we had up till then observed. The edges of the upper stratum of clouds gradually lighted up, and we soon saw isolated flames issuing from them that sometimes rose to the zenith. Suddenly, the phenomenon embraced the entire horizon. Everywhere were flames, everywhere were jets of brilliant light, yellow below, green in the center, and reddish violet above. In an instant, all the rays united in a regular and dazzling crown, situated in the heavens to the south of the zenith. When the phenomenon reached the maximum of its intensity, it reminded us of the immense vault of a temple, with a brilliant chandelier in the center. The apparition lasted but a few minutes, but, on vanishing, left behind it a luminous zone between the banks of clouds. From the upper bank there continued to emanate, at short intervals, isolated rays that rose to the zenith, and there formed the fragments of a crown. The edges of the banks of clouds remained luminous, although the rays had disappeared."

According to Mr. Lemstrom, Fig. 1 gives an idea, although a feeble one, of the phenomenon at its height. It reproduces only half of the horizon, and the reader may supply the missing portion of this grand spectacle in imagination. The streams of light verging toward a common center were alternately rose colored and pale yellow, and overlooked an immense violet zone. The rosette in the center was of a beautiful red, and stood out upon a greenish blue circle.

Fig. 2 represents an aurora that was observed on the 19th of November, 1871, in Finnish Lapland. At the beginning, and at 30° above the horizon, it formed an arch from whence rose waves of light, and which gradually ascended. The figure shows it when it had reached about 60° above the horizon. The base of the aurora was yellow, and the oblique and very brilliant rays were, slightly higher up, rosy, violet, and blue. The colors of the polar light are usually clear and bright, but never did they exhibit greater luster than on this occasion.

Fig. 3 gives an idea of the variety of forms that the phenomenon may affect. It represents an aurora that was observed at the presbytery of Enare on the 16th of November, 1871. The aurora this time took on the form of a glowing red band, curved as shown in the figure. The two extremities bordered on yellow and green.

There is another form of aurora frequently observed in northern countries, and that is the one that is seen to occur above clouds, and that has the appearance of a wide piece of drapery with undulating folds. As it is the form most usually represented, we shall not dwell upon it. On the contrary, we shall speak of other phenomena of the same origin, and much less known, that Mr. Lemstrom describes. It concerns those auroral lights that shine at the edges of clouds, or that form around the tops of the mountains in Spitzbergen or in the Alpine districts of Lapland. According to the Finnish observer, it would be impossible to tell by the naked eye whence this light comes, but, by means of a spectroscope, we find that it is of the same nature as the aurora. Sometimes, these strange lights take on the form of flames of but little brightness, which, at short intervals, rise from the crest of the mountain and suddenly vanish (Fig. 4).

These phenomena sometimes exhibit themselves at the level of the earth's surface, or upon the roofs of houses.

Finally, Mr. Lemstrom describes the diffuse light which sometimes fills the atmosphere of the polar regions, thus proving that the phenomenon shows itself from time to time in the vicinity of the earth itself.

Meteors of the same nature as the light of the auroræ boreales do not occur solely in the polar regions, and the author demonstrates, not without attaching much importance to it from the standpoint of the theories to which he has been led, that they are observed in other countries of the earth. In Peru, Bolivia, and Chili the summits of the mountains are often seen illuminated by a brilliant light. This light, which occurs especially in summer, has been compared to heat lightning by scientists.

Similar observations have been made in the Swiss Alps. Dr. De Saussure has seen electricity escape through all the projecting parts of objects, and the same phenomena have been observed upon the high plateaus of Mexico. Again, we may cite the fact that Brewster observed a light upon a church tower during an aurora borealis. In every country phenomena similar to polarized light may occur.--_La Nature_.

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IN 1886, 17 Gloucester fishing vessels were lost, worth $115,800, and 115 fishermen never came home. The year was remarkable for the small inshore catch, almost all the fishing being done on the high seas.

The Latest Yankee Craze.

At the forthcoming American Exhibition in London, we are promised, among other novelties, a house of straw, which is now being made in Philadelphia. This house is to represent an American suburban villa, announced to be "handsome and artistic in design," two and a half stories high, and covering a space of 42 feet by 50 feet. It is constructed entirely of materials manufactured from straw--foundations, timbers, flooring, sheathing, roofing, everything in fact, including the chimneys--the material being fire proof as well as water proof. The inside finish is to be in imitation rosewood, mahogany, walnut, maple, ash, ebony, and other fine woods, the straw lumber taking perfectly the surface and color of any desired wood. This straw house is, in the first place, to illustrate Philadelphia's commercial, financial, and industrial interests by means of large photographs of the leading buildings; but it will also demonstrate how far the inventive Yankee has succeeded, not in showing us how to make bricks without straw, but how to produce timber from straw. If, after this brilliant exhibition of inventive genius, we do not bow down and worship him as the "licker" of creation, we may consider ourselves lost to all sense of what is proper under the circumstances.--_Iron._

EFFECT OF A TORPEDO ON AN IRONCLAD.

The British government lately strengthened up the bottom of the old ironclad Resistance, and tried the effect of firing off a 90 lb. guncotton torpedo against the vessel. To the surprise of every one, the ship was not seriously damaged. The _Engineer_ comments upon the experiment as follows:

The Resistance experiments so far tend to demonstrate that the total disablement or destruction of a modern ironclad is not so easy as many people imagined. It was too hastily assumed that the explosion of a charge of 90 lb. of guncotton in contact with any portion of the hull under water would have such destructive effect as to overcome the protection afforded by a thick lining of coal and the cellular system of construction now always adopted in vessels of war. There are, however, certain considerations attached to this experiment which, if duly weighed, should reassure the advocates of the torpedo, and restrain the exultation of naval architects within reasonable bounds. We shall endeavor to place these before our readers briefly and impartially, reserving a fuller summing-up until the remaining experiments are concluded, as they are of greater importance than any of those preceding. It is the more essential to do this because the _Times_, in a leading article of November 3, leads us to believe that as this attack failed, in the broad sense of the word, similar attempts under different conditions would have a like result: and that although serious damage would be caused, the ship would remain "floating and seaworthy, with her offensive powers not materially impaired." We are not prepared to accept this conclusion, for the following reasons:

First, let us consider the general effect of a submarine explosion. It closely resembles the action of gunpowder when ignited in a gun. We know that in the latter case a quantity of heated gas is formed, which in its power of expansion exerts force in all directions. Prevented from expanding by its rigid confinement, except in the direction of the bore, the gas attains its object by the displacement of the projectile. This is, in fact, the line of least resistance. When the same explosive is ignited under water, the heated gas presses outward in all directions, forcing the surrounding molecules of water against their neighbors, which are, in turn, propelled forward with great violence. This effect continues until the back pressure of the liquid medium equals the now reduced pressure of the gas due to its expansion in the space vacated by the displaced water, which is likewise to some extent compressed by the action of the gas. Though brought actually to a state of rest, the surrounding water is under the influence of great pressure, which by the law of fluids is transmitted equally in all directions. When a vessel is sufficiently near the explosion to be struck by the water which has been so violently disturbed, it will act upon her like a huge projectile, and it is obvious this range will be in proportion to the amount of explosive employed. This, combined with the resistance her hull offers, will also determine the effect produced.

If the charge is too near the surface of the water, the liquid layer above it will not restrain the liberated gas sufficiently to allow of its full power being exerted in other directions, and hence permits its escape into the atmosphere, throwing up the water in its way to a greater or less height, according to the thickness of the layer. The spectacular effect, therefore, afforded by the upheaval of a large and lofty column of water is no criterion of the efficiency of a submarine explosion, but, on the contrary, shows that much of its energy has been expended in the wrong direction. The amount of submersion to give the greatest lateral effect to different charges of explosive has been ascertained by practical experiments. For 100 lb. of gunpowder, it is stated to be 10 ft., while for the same quantity of guncotton it should be 15 ft. As the charge employed against the Resistance was 90 lb. of guncotton placed 10 ft. below the surface, it is probable that some loss of power was sustained in the manner we have indicated. At a greater depth also the charge would have been to some extent under the vessel, where its explosive effect would have been more severe, and where the construction of the hull cannot be as strongly fortified with coal as was the case in the Resistance. We are unable to state why a depth of 10 ft. was selected on this occasion; but it may be due to the fact that up to a late date most of our locomotive torpedoes have not carried a larger charge than 40 lb. of guncotton, and are usually run at 10 ft. below the surface.

Considerable stress has been laid on the fact that in this experiment the charge was in actual contact, and yet did not effect complete penetration. It is even gravely asserted that an actual torpedo would have rebounded a certain distance before explosion took place, and this would diminish its effect. In the first place, the detonation of guncotton is practically instantaneous, so that impact and explosion would be simultaneous. We are hardly prepared to allow an inch rebound, but will concede that until actual proof convicts us of error. In the second place, it is possible that a distance of three or four feet between charge and ship would rather augment than diminish the effect produced in the case of such an explosive as guncotton when sufficiently immersed. It is possible the intervening water thrown against the side of the ship would do more damage than the gas liberated in actual contact. At any rate, experiments some years ago with smaller quantities of both dynamite and guncotton showed that when exploded 4 ft. from the bottom of a ship, enormous damage was inflicted on her.

Although it is generally estimated that guncotton is about four times more powerful than gunpowder, this does not appear to hold good under all conditions; while, on the other hand, for certain purposes, ten times the amount of gunpowder would not produce the same result. This is proved by the ease with which the strongest chain cable and wire rope can be ruptured by a small charge of guncotton, which even more than ten times the amount of gunpowder could not accomplish. This is due to the peculiar shattering action of detonated guncotton, which the slower burning substances does not possess, its characteristic being more of the nature of a push than a blow. Taking into consideration the method in which the hull of the Resistance had been strengthened for this experiment, and the exact locality chosen for the explosion, it is probable that less than twice the amount of gunpowder would have caused a more complete breach through the coal protection. The torpedo is stated to have had everything in its favor; whereas, in our opinion, all the advantages were on the side of the ship. The attack was made at her strongest point, where the coal was specially disposed, and her shape under water lent no assistance to the explosive. To assume from this that if a similar torpedo struck lower down, or further aft, or against the propeller, the ship would still have "her offensive powers not materially impaired," is to express an opinion with which few will be found to concur.

Under the alternative circumstances mentioned, half the amount of explosive might practically disable the vessel, though her flotation need not be overcome. Whitehead torpedoes need not necessarily be limited to a depth of 10 ft., as by slightly strengthening their construction they could be run 20 ft. below the surface. We presume it will be allowed that this would increase their destructive power, especially in the vicinity of engines and boilers, which now occupy so much space. In a similar manner there is no difficulty in increasing the charge of a locomotive torpedo to a point at which it becomes irresistible, whatever system of internal protection may be devised. This has, in fact, been going on for some time; more than one nation possesses torpedoes armed with 100 lb. of guncotton, and if we do not, it is simply because former experiments led us to believe sufficient damage would be caused by a less quantity. We can only consider that disproved on demonstration by further trials under conditions less favorable to the ship, and we venture to predict some delusions will then be dispelled which this particular experiment seems to have occasioned.

Steel Wire Brush Patent.

Before Judges McKennan and Acheson of the United States Circuit Court for the Western District of Pennsylvania, at Pittsburg, Pa., No. 16 of November term, 1886, a question arose as to whether a steel wire brush for cleaning castings, and a steel wire brush for cleaning boiler flues, was an infringement on what is generally known as the Wright patent, No. 59,733, and the reissue, No. 2,598, owned by Joseph McArthur, of New York city.

The Wright patent consists of a wooden block with a series of pairs of holes. A bundle of wire splints is doubled and the ends inserted in the holes, being held by the wooden bridge between the holes and by a wooden back screwed to the block.

Joseph H. Davis, of Sewickley, Pa., the defendant, under his casting brush patent, No. 232,600, the construction of which consists in the doubling of the wire splints and inserting in one hole of a wooden block, and fastening by means of weaving a wire through the loop, the wire being held in place by a wooden back fastened on by driving wrought iron nails through the block and back and clinching on the back, thus making the block and back practically inseparable.

The Davis flue brush patent, No. 181,416, is made by sticking the wire splints through holes in an iron cylinder, there being no wood about its construction.

Several cases had been tried in other States involving the validity of the Wright patent, which had resulted in Mr. McArthur's favor, but after exhaustive argument in the case at Pittsburg, Pa., the court held the Davis brush not to be an infringement on the Wright patent.

How Long Should a Nervous Patient be Treated?

The question of how long treatment should be continued in a neurotic case when no evident benefit is produced has recently been raised in a Hamburg law court. A medical man, says the _Lancet_, having as a patient a merchant suffering from "nervousness," treated him by galvanism. Altogether he galvanized him 445 times, but the nervousness did not disappear. Then came the matter of fees. The sum claimed was $556. The merchant disputed this on the ground that the treatment ought not have been continued so long, as it was not producing any benefit. The court referred the matter to the medical board, which gave as its opinion that the doctor ought to have asked the patient, after some fifty sittings, whether he would like to continue them, as it was doubtful whether the treatment was doing any good. The court, however, declined to accept this view, holding that it was for the patient to say when he had tried the treatment as long as he was disposed to pay for it, and so gave judgment for the full amount claimed. This judgment seems to accord with the principle that applies to newspaper subscriptions. A man must pay for his paper as long as he takes it from the post office.

TORPEDO BOAT ARMED WITH PNEUMATIC DYNAMITE GUNS.

In former issues of the SCIENTIFIC AMERICAN we have given illustrations and detailed descriptions of the pneumatic dynamite gun invented by Lieutenant E. L. Zalinski, of the U. S. Artillery Corps. This gun, it will be remembered, was designed to throw a projectile loaded with dynamite or nitro-glycerine by means of compressed air; and so successful were the experiments carried on with it at Fort Lafayette, under the supervision of a board of naval experts, that Congress eventually appropriated $350,000 for building a swift torpedo boat, large enough to go to sea, and to be armed with three of these guns. Contracts for this boat have been signed with the Cramps.

The upper view in the accompanying engraving is a longitudinal vertical section, the lower one being a plan view. The following details regarding the boat we take from the _Sun_. The boat will be 250 ft. long, 26 ft. beam, and will draw 8 ft. of water. Her displacement will be about 800 tons. The engines will be of the triple expansion type, of the best known design, and the guaranteed power will be 3,200. She will be propelled by twin screws, and it is expected that the guaranteed speed of 20 knots an hour will be exceeded.