i 1 organization. Aggregations of such cellular bodies irato large wholes is a still further advance. Again, when such wholes have certain individual characteristics, and these individuals are united together to form a compound structure, though still in a greater or less degree leading an independent Life as in sponges, we speak of such community as forming an organism higher in the scale than the others. Those little societies of monads or cells, or whatever else we may call them, are societies only in the lowest sense; there is no subordination of parts among them-no organization. Each of the component units lives by and for itself, neither giving nor receiving aid. There is no mutual dependence save that consequent on mere mechanical union."* Even when this "mixed jelly" or these cells constitute an organism, which we may safely call an individual, there is little of that structure which we usually associate with the idea of an animal. Now, here it may be well to remark that, although a strict definition of the terms higher and lower, and the application of them first to classes, and then logically to different individuals of these classes, lead us into strange absurdities and contradictions, yet it is evident we cannot dispense with them. The source of these contradictions we shall explain hereafter. Enough for the present that the common sense of mankind, basing its judgment on the principles which make one society, one human being superior to another, will affirm that the animal kingdom shows us gradations of rank; that a mollusc is higher in the scale than a sea-anemone, that a fish is superior to an oyster, an eagle to a spider, man to a dolphin or a whale. It is for us to indicate scientifically the general grounds of this distinction. We shall find that, in the main, they are the same as establish the difference between the orders of the vegetable kingdom, as also between the higher and lower social organism. When we examine the body of one of those compound polyps common to our ponds, we find a mere jelly-like sac in which there is great uniformity of structure; in which, as we have said, the outer tissue may perform the functions of the inner one, and vice versa; in which there is no digestive or respiratory apparatus, no heart, alimentary canal, circulatory or nervous system. We have little or nothing of that which has been aptly termed the physiological division of labour. But when we discover a difference between the internal and external covering, a step towards the development of organs of nutrition and of the apparatus of external action; when we find a duct for the conveyance of blood, a part of the body specially devoted to its aeration, a receptacle for the food, nerves to convey sensations, and to serve as sympathetic bonds between the different members, organs, or parts-thus making the exercise of each subservient to the well-being of the whole-we say there is an advance in the organization. The degree in which we find this complexity of structure, the differentiation of function, these varied phases of activity in any organism, shall be determinative of its rank. Therefore it is that the mollusc is higher than the coral polyp; that, of the mollusca, the cuttle-fish with osseous skeleton, with large eyes, strong muscles, a complicated digestive apparatus, and a well-developed brain, is higher than the snail or oyster; that the articulata, as a rule, are superior to the mollusca; that spiders, lobsters, crabs, bees, &c., are higher than whelks and limpets. which have peopled it in past ages, has been one That is to say, that in the earliest strata we do In that vast series of ages during which the strata which now form the dry land of the earth were gradually and slowly deposited by the waters, and then raised above the surface of the deep, epochs of greater or less duration have distinguishing characteristics. The systems of the geologist which denote these epochs, commencing with the earliest that were formed and ending with the more recent, are termed the Cambrian, Silurian, Devonian, Carboniferous, Triassic, Oolitic, Cretaceous, and Tertiary. Now let us glance at the forms of animal life which successively characterize them. it is the presence of his remains, or of his productions that now first find a place-have a genesis also and a becoming-in the evolution of that great organisin of which he is a part. Considering then such development as we have here indicated; the insensible gradation by which life has attained to its present "wide discourse;" how the inorganic has passed into the organic, mere sensibility to impression into instinct, instinct into intelligence, intelligence into moral ideas, and brute force into delicate organization; how the epochs of the geologist blend with one another, yet possess distinctive features, how the forms which characterize them, widely different as some of them are, may yet be traced back to a similar ancestry; how the lifeenergy of the world has thus fashioned for itself one language and one history, we cannot be insensible to the analogy which is suggested by it. The creative and productive energies of nature have stamped each epoch with a particular character, and that character is more complex as the years advance. Looking at the animal life of the world in its totality, its progression is analogous to that of an individual. Taking also the whole of its vegetable life, a similar unity in the plan of development is presented to us. That advance, from the simplest structures of the Laurentian and Cambrian rocks to the varied diversity of the vegetation of the present era, is typified in the growth of every tree in the forest. Protoplasm into cells, cells into folia, folia into axes, axes into branch-combinations-such in brief are the stages passed through by every shrub; and such appear to have been the stages through which plants of successively higher kinds have been evolved from lower kinds."* Neither Look again at the simple starchy mass whichi s the substance of the acorn, and notice the changes which it undergoes. When the influences of heat and light have initiated changes in its molecules, it is not a leaf or flower which is produced; the progress to these is so gradual that we cannot perceive where one state begins and another ends; when the germ is no longer a germ, but plumule and radicle; when the outer tissue of the former begins to assume the appearance of bark; when the first rudiment of the leaf is formed, and when the structure of the roots diverges from the stem. in the evolution of the whole vegetable kingdom can we perceive where the specific characters of one individual class or species begins, nor where, indeed, their influence ends. Vegetable progress, like all other, is continuous, is cumulative. Myriads on myriads of individuals have lived and died, and each has passed on to its successor the advantage it gained. The life of a large tree is a cycle involving other cycles. Each returning spring sees the renewal of its life, the summer its maturity, the autumn its decay. So has the vegetation of the earth, as a whole, had its period of commencement, its exuberant growth, and also its decline. But not only individuals, but vast groups of these, different species and genera, have had their genesis, have gradually attained their highest organization, their greatest perfection, become for a while the dominant forms of the plant-life of the earth, and then gradually disappeared. So have flourished and passed away, for instance, many of the species which form, in a great measure, our coal-beds.. They have now no representative in existence. Wheresoever we find the primary rocks, whether in the Ural mountains, in those of Wales or of Canada, in the Steppes of Russia or in the far west of America, there it is that the early traces of life commence in the coral-like masses formed by those microscopic animalcula which we take to be the lowest form of animal existence. Shells also of such minute and simple organisms as are at present found in the ooze of the sea, or amidst its waters. Later, we come to shells of the lower molluscs; crustacea analogous to the embryological forms of species which succeed them; the rocks occasionally reveal to us also the tracks and burrows of worms. But the evidences of life are yet somewhat scanty. The organisms themselves were perishable. The action of fire on the strata has more or less metamorphosed them. In the Silurian epoch, the aspects of life broaden; although the remains of no terrestrial animal have yet been discovered in it, sponges, corals, starfishes, higher molluscs and crustaceans abound. With the Devonian era we enter upon the predominance of gigantic crustaceans with complex limbs, and a corre spondingly complicated internal economy; but, above all, it is here that we meet with fishes for the first time. Shoals of them are imbedded in the strata, albeit of so simple a type of structure as to have been mistaken for crustaceans, and even huge water-beetles. In the Carboniferous, many of the lower forms of life already noticed have become more complex; their different species have more determinate and distinctive forms. The bone-encased fishes of the Devonian have given place to forms analogous to some which now are found in Australian seas. With the dry land which now seems to become more general, and the growth of the vast forests which at present afford us coal, the remains of beetle-like insects are discovered. Evidences of terrestrial life are also furnished by fish-like lizards, frog-like reptiles, and a linking and blending of aquatic and terrestrial life as manifested in the characters of Amphibia. In the Permian and Triassic systems we find true lizards and true reptiles abundant-some species of huge size and When the osseous skeleton which we have noticed of high organization. At the same time, the general in the cuttle-fish divides the body into two cavities, character of the forms of life contemporaneous one of which is specially adapted to the organs of with them has altered. The molluscs present greater nutrition and the other to the principal nerve- differences, the bone-encased fishes of the Devonian centres, with all the wonderful modifications such age have given place to others more resembling division implies, we have the vertebrate type of those now existing. Insects are more varied. We structure. This is an advance on the others, one have yet no evidence of true birds, but only of rep. 280. A, has permanently secured within it a which makes fishes, as a class possessing it, higher tiles walking bird-like on their hind feet; none of than insects, molluscs, and protozoa. Now a land true mammals, but only of those which produce animal being subject to greater differences of con- their young in so imperfect a state that it has been ditions than one which inhabits the sea, will, as a well said that it is a shell-less egg that is born-it rule, have corresponding differences in its struc- is marsupial-like animals, such as are allied to the ture, the limbs will be more diverse in their kangaroo, which precede the true mammals. In character, organs of nutrition adapted to more com- the Oolitic, reptiles abound to such an extent, plex nature of food; lungs with their myriad wade through the marshes, swim on the sea, fly interstices will have replaced gills; the blood will over the land, that it has been termed par excelbe warmer, the machinery for propelling it more lence the " 'age of reptiles." Traces of true birds complicated; the senses more acute, nerves more also become noticeable towards the close of this intricate, brain more developed. It is therefore that an amphibian is superior to a fish. On the epoch. But in the chalk these indications became same principle of more frequent, and here also are signs of the existmore complex organization, ence of true mammals. But with the Tertiary reptiles as a class present to us a higher type than epoch, while vast numbers of species which characamphibians, birds than reptiles, and a man, as terized the preceding ages have become extinct, representative of the mammalia, has an organism others take their place become as it were the domi decidedly more complicated as a whole than any bird. nant and special forms of existence. It is here that However much we may be at a loss when we consider all the details of the vast scheme of life ties of our museums-the Epiornis of Madagascar, the birds whose gigantic remains form the curiosithat has been developed on the earth; however the Dinornis of New Zealand-come on the scene; much the facts of geology, or more properly it is here that enormous mammals, as the Megathe paleontology, limited as they are, may seem to contradict some of our notions with regard to it; small as is the portion of the earth's crust that has been explored, or looking at the vast expanse of water on the globe, ever will be subject to the scrutiny of science, enough has been discovered to day. Myriads on myriads of individuals, nay thousands H, the lower edges of which, as well as those of show us that "the law of the genesis and becoming of the living forms which people the world now, and * H. Spencer, “The Social Organism," Essays. Vo.I. rium and Mastodon, are first discovered. The whole (To be concluded next week.) MECHANICAL MOVEMENTS. Another kind of gasometer. The vessel central tube a, which slides on a fixed tube b in the centre of the tank. As the 281. Wet gas meter. The outer case is stationary, The and filled with water up to above the centre. inner revolving drum is divided into four compartments, B B, with inlets around the central pipe a, which introduces the gas through one of the hollow journals of the drum. This pipe is turned up to admit the gas above the water, as indicated by the narrow near the centre of the figure. As gas enters the compartments B B, one after another, it turns the drum in the direction of the arrow shown near its periphery, displacing the water from them. chambers pass over they fill with water again. The cubic contents of the compartments being known, and the number of the revolutions of the drum being registered by dial work, the quantity of gas passing the supply of gas to all burners of a building or apthrough the metre is registered. 282. Gas regulator (Power's Patent), for equalizing partment, notwithstanding variations in the pressure on the main, or variations produced by turning gas on or off. to or from any number of the burners. The regulator-valve, D, of which a separate outside view is given, is arranged over inlet pipe E, and connected by a lever, d, with an inverted cup, valve, dip into channels containing quicksilver. There is no escape of gas around the cup H, but "Principles of Biology," vol. ii., p 214. e the amount of stiffness given to them, either by creasing the sectional area of metal in them, or dopting a form of section adapted to ensure the quisite rigidity. It will be at once apparent that he greater the number of the crossings of the bars e less becomes the actual length of any unsuported bar. Every intersection of two bars, suposing it to occur at the middle of their respective fngths, virtually reduces those lengths one-half, nd the stiffness of the bars is thus nearly doubled, >r while the original strain remains the same, the endency of the bars to deflect is very considerably iminished. This was one of the causes that -peedily proved how deficient the Warren system as in those points when girders of large span rere proposed to be constructed on that principle. t was soon discovered that it was absolutely imbossible to construct a deep girder with only one series of triangles. The amount of material that it vas necessary to introduce in order to afford the proper degree of stiffness to the bars was very much n excess of that which would be required in a solid-columns. sided or plate girder. It must be borne in mind that the superior economy of the open or lattice type of girder over that of the plate system rests in the web, and in the web alone. The flanges or horizontal members of both systems are nearly identical. If, in designing a large girder on the lattice principle, the saving is not effected in the web, it cannot be obtained in any other part. The section of the crane shown in elevation in Fig. 1 is represented in Fig. 2, and, with the excep tion of the web or sides, does not differ materially from that given in our last article. Directly the horizontality of the flanges is departed from the strains upon the bracing or bars connecting the upper and lower flanges, and constituting the web, become very complicated, and it is by no means easy to ascertain, without some slight consideration, which of them act as struts and which as ties. When we proceed to analyze the strains upon a bent crane, and the manner in which each separate bar is affected by the load, it will be demonstrated that those which slope towards the lower or fixed IT the other bars. But this is not sufficient, and one of 24 or 30in. in breadth. At the time of constructing the Britannia Tubular Bridge over the Menai Straits there was the greatest difficulty experienced in obtaining plates 12ft. in length. Since that time our iron manufacture has made a great deal of progress, but still long plates are very expensive. This is owing to a combination of many circumstances. In the first place, the larger the plate the greater the trouble and expense of handling and transporting it from one place to another. Secondly, the difficulty of rolling a plate or bar that shall be homogeneous in consistency increases enormously in proportion to an increase in the size; and thirdly, larger and more expensive rolling machinery is necessary than for plates and bars of the ordinary dimensions. Besides stiffening the bars in the web of the bent crane in the plane of the elevation of the crane, they also require some bracing in a plane at right angles to the face of the web. The opposite bars have to be braced together transversely, as shown in Fig. 2. This is usually effected by introducing small pieces of bar or angle iron, and riveting them (see A A, in Fig. 2) to the diagonals at their intersections with each other. Notwithstanding the salutary operation of this system abroad, however, and notwithstanding the peril from storms to which our commerce on the great lakes and the Atlantic seaboard is constantly exposed, no measures have been taken in this country, until within the past few months, for the inauguration of such a system here. Early in the present session of Congress, however, the matter was brought to the attention of the House of Representatives by the Hon. Halbert E. Paine, of Wisconsin, who offered in that body a joint resolutions at the military stations and other points in the interior of the continent, and for giving notice on the northern lakes and seaboard of the approach and force of storms." The resolution in full is as follows: extremity of the crane are subject to compressive united, not merely by horizontal pieces of bar, but tion providing "for taking meteorological observa strains, and, per contra, the others to those of a tensile description. But this is not a universal rule, for a great deal depends upon the radius of the upper and lower flanges, the depth of the web, and the angle of inclination of the bars. This angle is continually changing, which is the great impediment to the use of mathematical calculation for these examples of construction. In those instances where the flanges, both upper and lower, are horizontal and parallel to one another, the angle of all the diagonal bars is constant, and the calculation of the nature and amount of the strains may be effected either by geometrical diagrams, or by simple and readily deducible formula. But directly either or both of the flanges assumes a curvilinear outline this simplicity of calculation is at once lost. The ordinary formulæ are no longer applicable, and those that would theoretically apply to each particular case in question are so exceedingly trouble. some, complicated, and uncertain, as to be prac tically useless. It is not too much to assert that to attempt to employ algebraical or mathematical equations and formule to some of the examples of girder construction would be to attempt a practical absurdity. Recourse is therefore had to the graphical method, and by means of a diagram of strains the proportions of the several parts can be accurately determined. At present we are not concerned with this part of the subject, which will be fully discussed in a subsequent article. In large examples, the opposite diagonals are by a regular system of cross bracing, so as, in fact, to convert the whole couple of diagonals into a small braced girder of itself. Wherever the depth of the girder is small this is not needed, but the plan shown in Fig. 2 will afford all the security required, We must reserve for the next article on the subject the investigations into the strains upon these braced specimens of construction.-Building News. contact. "Be it resolved by the Senate and House of Representatives of the United States of America in Congress assembled, That the Secretary of War be, and he hereby is, authorized and required to provide for taking meteorological observations at the military stations in the interior of the continent, of the United States, and for giving notice on the and at other points in the States and Territories northern lakes and on the sea-coast, by magnetic telegraph and marine signals, of the approach and force of storms." old method of cauterization by fire is to be replaced by USE OF ELECTRICITY IN CAUTERIZATION.-The the electro-thermic or galvano-caustic apparatus. The latter process is safer and more certain in its operation. It is possible at will to vary the degree of heat, to raise it instantly to the highest intensity, to diminish or sup press it, to render it intermittent or continued, to direct This resolution was promptly passed by both it into deep cavities, and to destroy all the tissues by houses of Congress, and on the 9th of February, electricity are less liable to contagion and miasmatic in- By General Orders No. 29 from the head-quarters It is said that the wounds produced by 1870, became a law by the approval of the President. fections than those caused by sharp instruments. The of the army, dated March 15, 1870, the chief signal apparatus can be made of any desired shape so as to be applicable to all parts of the body, and it is known that officer of the army, Brevet Brigadier-General A. J. important cures have been effected by the introduction Myer, is charged, subject to the direction of the of parts of the body inaccessible in any other way. visions of this enactment, and all commanding of platinum wires and the cauterization by the battery Secretary of War, with the execution of the proElectricity has already been tried in cases of bad tumors, officers are enjoined to afford every facility for the in amputations, in excisions of cancers, in destruction of wens, for opening cysts, for removing internal tumors, successful prosecution of the undertaking; while upent article in Cosmos claims for it the following ad- and others, are requested to aid, by their co-operawounds by fire, and in numerous other cases. Ascientific establishments, commercial associations, A reference to Fig. 2 will show that a plain bar vantages: The electro-thermic cautery suppresses all tion, in the accomplishment of the work. section will not answer for the compressive bars the retention and alteration of the liquids; avoids all pain after the operation; avoids loss of blood; prevents in the web of a bent crane. This is owing to the putrid and purulent infections; facilitates the organic fact that a plain rectangular bar has little or no reconstruction and healing of the parts; affords a lateral stiffness. It is true that when occupying method universally applicable, strong or weak, conthe position of one of the diagonals in the web of tissues, of carbonizing them, of destroying them, of con intermittent; capable of sloughing the a girder designed on the lattice principle, it is verting them into gas, and must be regarded as one of the most important contributions to modern surgery." stiffened to some extent by the intersections with tinuous by the frightful aggregate of a single year's disasters Professor J. A. Lapham, of Milwaukee, impressed to vessels on the great lakes-amounting for the year 1869 to the immense number of 1,914, with an estimated damage to property of over four millions Extracted from an article by L. A. ROBERTS in the Western Monthly. of dollars-was perhaps the first to suggest some action by Government for inaugurating such a system of storm-reporting as, through the efforts of General Paine, has now happily been adopted. It should be remarked that by no means all of the disasters included in the aggregate above given were of that class which might have been obviated by the operation of the system we are considering. Very many were due to imperfect machinery, defective boilers, careless collisions, conflagrations, and other causes. Yet, making all proper deductions on this score, enough remain to be attributed to the destructive force of severe and unheralded storms, to fully justify any action by Government looking to a mitigation of the destruction of property and the peril and often loss of life which they entail. No corresponding statistics are at hand as to the yearly disasters upon our Atlantic seaboard; but these are very numerous, as is well known, and of these a much larger proportion than of the lake disasters are attributable to the agency of storms. Besides the great equatorial storms already alluded to, which in their course towards the pole follow approximately the coast-line of the United States, our coasting vessels are likewise exposed to frequently-recurring tempests, especially in the summer season, which originate probably upon the great desert basin in the interior of the continent, and, sweeping eastwardly across the Mississippi Valley and the great lakes, expend their final fury upon the ocean and its navigators. Nor must damage often worked down, crushing the horses and burying himself to Unless this adhering layer of air is (To be concluded next week.) CEMENTS AND HOW TO USE THEM. GREAT deal has been written concerning 190 CARBON PRINTING ON ENAMEL & AND PORCELAIN SURFACES THE production of a carbon opalon on land, as well overpon the water, by these latter A different cements, and indeed our periodicals almost any moderate amount of labour in one storms, and by those tornadoes of narrower limit and shorter duration, but often of even greater intensity, which prevail at intervals throughout the Mississippi Valley, and lay waste the narrow belt of country which they traverse. Of this class was a storm which swept through Northern Ohio and on the Alleghany Mountains in Pennsylvania in the summer of 1855, demolishing very many buildings in its course, uprooting trees and razing fences, and causing the death of many persons. So furious was this storm, and yet of so limited a breadth only about an eighth of a mile-that while in some villages over which it passed scarcely a house escaped damage, in others only the northern or southern section of the town would be devastated; the outer verge of the destructive force being so sharply defined that while one house, that fell within its track, would be almost totally destroyed, another, but a few yards distant, would be wholly unharmed. The course of this storm may even yet be easily traced in the forests through which it raged. It cut a clean swath as it went, leaving openings that look as if they had been cleared for a highway or a railroad. The timber thus prostrated was in some cases utilized for firewood or for lumber; but in many places the trunks of the trees were left in such inextricable confusion and tangle-having fallen in every conceivable direction, and being in some instances individually twisted into splinters, as a result of the rotary action of the storm-that it was found inexpedient, in a country where timber was in plenty, to attempt to "pick up the pieces;" and thus the logs were left to rot and replenish the earth. And now, throughout these storm-openings in the woods, vast thickets of the highbush blackberry have grown up; and so we have, as the latest result of that furious tempest, an almost unlimited abundance yearly of the finest blackberries anywhere to be found. No one who has witnessed such a storm as this will ever forget it. The imminent peril of a storm at sea may be greater and more appalling; but nothing can be more exciting than one of these fierce whirling tornadoes, accompanied, as they almost always are, by a deluge of rain and an almost constant rolling of thunder and glare of lightning. The storm is heralded by a heavy mass of cloud in the west or southwest, dark, with a sulphurous tinge, over the face of which there is an almost constant play of lightning, and within an ominous muttering of thunder. Then there is a dash of rain, a moaning of the wind, and the next moment the storm bursts upon you. Then the air is full of a tumult of unwonted sounds. Loose shutters, sign-boards, and what not, are dashed against the house. Chimneys are blown into individual bricks, and the bricks come clattering down the flues. Doors and windows are burst open; the house trembles to its foundations; and the next moment you behold your roof following your neighbour's in a wild flight for the open countrygoing to pieces as it is borne along like a wreck upon the sea-scattering its fragments broadcast, some of them being found afterwards miles away. Such unfortunate persons as chance to be abroad upon the streets when the fury of the tempest is let loose, strive in vain to make headway either with or against the current, and can do no better when blown to the ground than lie prone there and thank their stars if nothing more pitiless than the drenching rain shall fall upon them; for factory chimneys and church spires go down like grass before the mower, and walls are falling on all hands. One poor man, seeking to rescue a span of valuable horses that are hitched to leeward of a house wall that he fears may fall, is too late; for even while he is in the act of untying the halter the wall is are full of recipes on this subject. But it will be found that the information given is rather in regard to the materials used in compounding these cements than in regard to the manner of using them. And it is unquestionably true that quite as much depends upon the manner in which a cement is applied, as upon the cement itself. The best cement that ever was compounded would prove entirely worthless if improperly applied. We have hundreds of recipes for glues, pastes, and cements of different kinds, and yet the public is constantly on the qui rire for new ones, and no more acceptable recipe can be sent to our popular journals than one for a new cement. Now, the truth is, that we have cements which answer every reasonable demand, when they are properly prepared and properly used. Good common glue will unite two pieces of wood so firmly that the fibres will part from each other rather than from the cementing material; two pieces of glass can be so joined that they will part anywhere rather than on the line of union; glass can be united to metal, metal to metal, stone to stone, and all so strongly that the joint will certainly not be the weakest part of the resulting mass. What are the rules to be observed in effecting this? The first point that demands attention is to bring the cement itself into intimate contact with the surface to be united. If glue is employed, the surface should be made so warm that the melted glue will not be chilled before it has time to effect a thorough adhesion. The same is more eminently true in regard to cements that are used in a fused state, such as mixtures of resin, shellac, and similar materials. These matters will not adhere to any substance unless the latter has been heated to nearly or quite the fusing point of the cement used. This fact was quite familiar to those who used sealing-wax in old days. When the seal was used rapidly, so as to become heated, the scaling-wax stuck to it with a firmness that was annoying-so much so that the impression was in general destroyed-from the simple fact that the sealing-wax would rather part in its own substance than at the point of adhesion to the stamp. Sealing-wax, or ordinary electrical cement, is a very good agent for uniting metal to glass or stone, provided the masses to be united are made so hot as to fuse the cement, but if the cement is applied to them while they are cold it will not stick at all. This fact is well known to those itinerant vendors of cement for uniting earthenware. By heating two pieces of delf so that they will fuse shellac, they are able to smear them with a little of this gum, and join them so that they will rather break at any other part than along the line of union. But although people constantly see the operation performed, and buy liberally of the cement, it will be found that in nine cases out of ten the cement proves worthless in the hands of the purchasers, simply because they do not know how to use it. They are afraid to heat a delicate glass or porcelain vessel to a sufficient degree, and they are apt to use too much of the material, and the result is a failure. The great obstacles to the junction of any two surfaces, are air and dirt. The former is universally present, the latter is due to accident or carelessness. All surfaces are covered with a thin adhering layer of air, which it is difficult to remove, and which, although it may at first sight appear improbable, bears a relation to the outer surface of most bodies different from that maintained by the air of a few lines away. The reality of the existence of this ad. hering layer of air is well known to all who are familiar with electrotype manipulation. It is also seen in the case of highly polished metals, which may be immersed in water without becoming wet. bably one of the easiest feats in plac printing of any kind. Not so, bower printing on a rounded or convex surface, s enamel tablet of the usual kind. This is with some difficulties, but they are not of v nature as to prove insurmountable: morem extreme beauty of a picture on a couves a surface is such as to justify the expec overcome them successfully. To do this modifications in the process are requisite first and most important one is to procure a ther much more flexible than any hitherto mas; by flexibility we do not here allude to the palate. sensitive film itself, but to the paper wed. employed as a means of support for that gater The commercial tissue that we have hitherteen using in our experiments has a hard, stif pars its foundation, and if tried for the purpose let proposed will require more than ordinary ensure a successful result. When trying some experiments with a we writing of the present article, we made se! ht on a basis of thin and imperfectly-mei Whereas the ordinary commercial tissue was so hard and brittle as to admit of its being broke, this, although when dry still stiff and any was devoid of brittleness, and after a brit song in water became quite limp and flaccid. Tablas is one of the main conditions of success out a carbon printing process upon ar face. With these explanatory observat proceed to give such instructions as enable any careful experimentalist to succed First of all, make a reverse cast the face of the enamel tablet. This may be are either in gutta-percha or plaster of Paris. I object of this will be seen as we proceed. Now, having a sheet of sensitized tissue placed on the paper in the darkened room, of course), lay upon it the enamelled tale on which it is intended to make the picture, and by means of a penknife or a pair of scissors, cua pigmented paper to the exact size. Now e this in the printing frame under the negati observe that in the subsequent operations a can be more easily manipulated than if the be printed up to the margin. The reason has already been stated. The pigmented p being removed from the printing-frame, is p cold water, and in the course of a minute becomes quite pliable. It is now laid carefully upon the enamelled tablet and covered with p of blotting-paper, which ought also to be cut to le same size. The mould of gutta-percha or plaster of whic have already spoken is now carefully laid do upon the top of the paper, which then indines the exact form of the enamel convex surface. is also retained in close contact with it. W very pliable tissue and a very slightly-rounded face, contact may be made by means of the squee but with enamels of the best form this cannot done. In this case, the means we have here descobe or some method analogous must be had recourse t When the paper has become partially dry method of development is precisely similar to t recommended in the former article on transparen printing-viz., immerse the tablet first in cold wa for a short time, then in water of nearly the t perature of 100° Fahr., and, after removing paper, continue to allow the hot water to f backwards and forwards over the surface every detail be perfectly visible. Now, before picture is allowed to dry, immerse in a weak solut of alum, and finally rinse in water and dry. T resulting picture will be quite equal in respect beauty to anything that can be done by burning and at the same time it will be quite as durab except with regard to mechanical injury. The brilliancy of the picture is enhanced by flowing over the surface some clarified albumen and then immersing it in water sufficiently hot coagulate this varnish. We have tried o varnishes-among them amber and chloroformwith good effect. No person except an expert can distinguish etween a picture produced by the method described ad one that has been burnt-in in a muffle.-The British Journal of Photography. EXPERIMENTS ON THE RESISTANCE OF author UNDER this title timents, made with the greatest care during a period of twelve years, which verify his theoretic views upon the laws of resistance of these materials. We lay before our readers the author's statement of the laws and their consequences. He says: one direction, total strain......180ctr. of which not more than 150 etr. should be due to the For unhammered cast steel, .120 etr. .330 ctr. of which not more than 220 ctr. should be due to the passing load. The constants apply to pieces of uniform section. The rupture of material is the consequence of -repeated vibrations, none of which reach the absolute limit of resistance. The differences of the tensions which limit the vibrations are therefore The proportional to the disturbance of cohesion. absolute magnitude of the limiting strains is effective only as it diminishes the difference attendant npon increased strain, which difference causes rup-breaking resistance, if the play of the spring is ture. The tensions and compressions affecting the same fibre are considered as respectively positive and negative; so that the difference of extreme strains is equal to the greatest tension plus the greatest compression. The following exhibit of the results of experiments illustrates the effect of this law of resistance. With reference to resistance to bending or tension, Wbrations may occur within the following limits of safety for each (German) square inch of section : Iron........ Between + 160 ctr. and Experiments with spring-steel show that carsprings should not be loaded to three-fourths of the small in proportion to the entire deflection. With a constant strain of 900 ctr. a play of between 900 to 1,200 etr. is allowed. MADE. paper or glass is fixed upon the upper end of the tube. Heat being applied to the bulb, drives out the air through the mercury, the latter, as soon as the bulb is allowed to cool, descends through the tube, being forced by the pressure of the external atmosphere. The upper end of the tube is then heated and drawn out, ready to be sealed hermetically. The mercury is then boiled in the bulb, to expel all trace of air, and while it is in a state of ebullition, the tube is sealed by directing the flame of a blowpipe against the upper end, which fuses the glass and closes the aperture. The reader must not imagine that all the manipu lations we have described are performed on all thermometers in a perfect and accurate manner. A very large majority of these instruments in common use are entirely worthless for any scientific investigation, although they furnish, perhaps, suffciently accurate indications for the regulation of the temperature of apartments, and for other ordinary purposes.-Scientific American. T the fourth monthly meeting of this society, Mr. D. W. Kemp delivered the first of a series of lectures on "Experimental Chemistry." In introHOW MERCURIAL THERMOMETERS ARE ducing the subject he said he had often been impressed with the value of the advice tendered in that extract from Montaigne's Essays which prefaces the "CorreENGLISH MECHANIC, and held it as a matter to be despondence" columns in the ever-increasingly-valuable plored that the correspondents in many cases seemed to entirely overlook it, and hence indulged in funny epistles pregnant with "froth"-not even the creamy, healthy froth which precedes and accompanies the flow of genial, heart-inspiring liquid, but more nearly resembling the vapid effervescence from a sick man's o'er-laboured stomach. Astroment. A small glass tube, with a bull MERCURIAL thermometer is a very simple at one end, containing mercury, and a graduated scale, constitute all that is essential to it; yet in 160 ctr. this, as in many other cases, simplicity begets difficulty. To make this simple combination perform + 240 its duty accurately is by no means an easy matter. The first difficulty met with is the want of uniformity in the diameters of the bores of different tubes, and the varying size of the bore in almost every tube. It is scarcely possible ever to find one the calibre of which is the same throughout its length, and, if so found, it is the result of pure accident. It is obvious, therefore, that unless some With reference to resistance to shearing:means of eliminating the errors which would arise Between 220 ctr. and 220 ctr. from this source be adopted, nothing like accuracy + 440 Of course the greatest fibre-strain actually applied is always less than the absolute breaking limit. The following are presented as immediate results of this law: Those parts of construction which act positively and negatively, as piston-rods, walking-beams, and the like, must be stronger in the ratio 9:5 than those which are strained in only one direction, as beams, bridges, roof-timbers, &c. In determining the resistance of bridges and large trusses the weight of the structure, since it forms an absolute constant minimum load, may be left out of account, provided the sum of the effect of proper weight and load does not pass the limits of elasticity. In the case of car-springs the vibrations are between limits whose difference is quite small compared with the maximum tension; hence the coefficient can be taken larger than in ordinary cases if the steel does not suffer an inch strain of more The method employed to obviate this difficulty is called "calibration." Tubes are selected tolerably free from imperfections, and a column of mercury, of one inch or less in length, is introduced into it. The tube is then attached to the frame of a dividing engine, and put in connection with flexible rubber bags, to which pressure is applied, and regulated by screws. The air pressure in one bag being reduced while it is increased in the other, the mercury column may be forced to and held at any part of the tube. Turning to the subject proper the lecturer began by remarking that the chemistry of the moderns is but the alchemy of the ancients in a further state of development. That whereas the ancients had divided all material things into four grand divisions, Fire, Air, Earth, and Water, chemistry in these days bodies, and, what is of more practical importance, had had sub-divided those into upwards of sixty simple shown how the various elements may be best turned to advantage in the vast workshop of mankind. He then referred at considerable length to the nomenclature and notation of chemistry, explaining and illustrating by experiment the difference between mechanical and chemical elements and compounds. During the remainder of the lecture he confined himself solely to the gas oxygen, and by several very interesting and beautiful experiments showed, in a striking manner, its capabilities of supporting combustion. The lecture was listened to throughout with the most rapt attention, and at the close several questions were put by the members, some of which were answered by Mr. Kemp. It was announced that at the meeting in September the president would deliver an address on "The Air we Breathe." Mr. C. E. Gordon was appointed to that post pro tem. The mercury being thus brought to the portion of the tube where the graduation is proposed to commence, the exact position of one end of the column is marked upon the tube, a microscope with cross in performing the operation with exactness. By wires being employed to aid the eye of the operator forced along until the end of the coluran, where the means of the rubber bags the mercury is again first mark is made, is brought under the microscope cross wise, placed at the other end, and so on Report of Observations made by the Members during the than 800 ctr. It often reaches 900 to 1,000 ctr.; act. The required dimensions of the bulb are found, approximately, by weighing a measured length of the mercurial column, and computing the capacity of the bulb from the known expansion of mercury and its specific gravity. THE OBSERVING ASTRONOMICAL SOCIETY. period from July 7th to August 6th, 1870, inclusive. SOLAR PHENOMENA.-Mr. Thomas G. E. Elger, of Bedford, reports that the sun's spots observed in July exceeded in number those recorded during the previous month, but they were, with a few exceptions, small (less than 30" in diameter), and although pretty equally distributed between the two hemispheres, those to the south of the sun's equator presented a remarkable contrast both in type and size to those observed to the north of it; the former, as in June, included some large scattered groups and moderately sized spots of The effect of strain is entirely different, if it is the normal class, while the latter consisted chiefly of constant and static, from the effect when it is variable and productive of vibrations. It is also solitary specks, without penumbra, and clusters of miimportant to consider whether a structure is in nute black punctures, which frequently assumed very grotesque configurations. A striking feature of the tended to serve a purpose for a limited period, or large groups observed during the early part of the to stand for an indefinite time. It follows that like factors of safety do not suit all constructions. In The bulb may be formed upon the tube previous month was an evident tendency either to close up, or In the to become dissociated upon reaching a certain position every case two factors are necessary; one, which to the calibration, or afterwards attached. determines the ratio of absolute breaking strength; former case, however, the thermometers have their on the disc about half way between the E limb and the On the 25th one of the largest groups obanother, which fixes the ratio to the vibration that ing and boiling points, and no tubes can be used served this year appeared at the E limb. On the 28th except such as are found to be approximately perfect. it measured nearly 5 in length, and consisted of a In the latter case, the arbitrary scale, as marked from large preceding spot 1'10" in diameter, followed by This group dwindled the calibration, may be reduced after the determi-a draggling train of "wispy" penumbra, enclosing very rapidly after the 28th. nation of the freezing and boiling points into the several small spots. Fahrenheit scale, by the application of a simple about 50 in diameter, was observed from July 13th algebraic formula. Fresh groups observed in the sun's N. hemisphere induces rupture by indefinite repetition. |