« ZurückWeiter »
in organization. Aggregations of such cellular bodies into large wholos is a still further advance. Again, when such wholes have certain individual characteristics, and these individuals are united together to form acompound structure, though still in a greater or less degree leading an independent life as in sponges, we Bpeak 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 inLrts among them—no organization. Each of the component units lives by and for itself, neither giving nor receiving aid. There is no mutual <lui>endencc save that consequent on mere mechanical union."* Even when this "mixed jelly" or these cells constitute on 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 lutoer, and the application of them first to classes, mid then logically to different individuals of these classes, lead us into strange absurdities and contrailictions, yet it is evident we cannot dispense with fthem. 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 on 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 bceu aptly termed the physiological division of labour. But whin 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—wo 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.
When the osseous skeleton which we have noticed in the cnttle-fish divides the body into two cavities, one of which is specially adapted to the organs of nutrition and the other to the principal nervecentres, with all the wonderful modifications such division implies, we have the vertebrate type of structure. This is an advance on the others, one which makes fishes, as a class possessing it, higher than insects, molluscs, and protozoa. Now a land animal being subject to greater differences of conditions than one which inhabits the sea, will, as a rule, have corresponding differences in its structure, the limbs will be more diverse in thencharacter, organs of nutrition adapted to more complex nature of food; lungs with their myriad interstices will have replaced gills; the blood will be warmer, the machinery for propelling it more complicated; the senses more acute, nerves more intricate, brain more developed. It is therefore that on amphibian is superior to a fish. On the same principle of more complex organization, reptiles as a class present to us a higher type than amphibians, birds than reptiles, and a man, as representative of the mammalia, has an organism decidedly more complicated as a whole than any bird. However much we may be at a loss when we consider all the details of the vast scheme of life that has been developed on the earth; however much the facts of geology, or more properly paleontology, limited as they arc, may seem to contradict some of our notions with regard to it; small as is the portion of the earth's crust that has b^en explt red, or looking at the vast expanse of water on tne globe, ever will be subject to the Bcmtiny of science, enough has been discovered to show us that" the law of the genesis and becoming of the living form9 which x>eop!e the world nuw, and
* II. Spencer, " The Social Organism," Easnys. Vo . I.
which have peopled it in past ages, has been one with that of the vegetation which has accompanied them, one with that of man and society which has in a measure come after them."
That is to say, that in the earliest strata we do not find remains of such complex organizations as share the" earth with man to-day, and whose structure is more or less allied to his own; nor, as we hove said, do we find there either a vegetation with that wonderful diversity of form and colour which delights, and in delighting educates and develops the refined and subtle faculties of the human mind. The whole course of creation has been oue harmony of power and form.
In that vast series of ages during which the strata which now form the dry land of tho earth were gradually and slowly deposited by the waters, and then raised above the surface of tho 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 tho Cambrian, Silurian, Devonian, Carboniferous, Triassic, Oolitic, Cretaceous, and Tertiary. Now let us glance at the forms of animal life which successively characterize them.
Wheresoever we find the primary rocks, whether in tho Ural mountains, in those of Wales or of Canada, in the Steppes of Russia or in tho 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 wo take to be the lowest form of animal existence. Shells also of such minute and simple organisms as are at present found hi 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 tho tracks and burrows of worms. But the evidences of life are yet somewhat scanty. The organisms themselves were perishable. The. action of firo on the strata has more or less metamorphosed them. In tho Silurian epoch, tho 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 correspondingly complicated internal economy; but, abovo all, it is here that we meet with fishes for the first time. Shoals of them ore 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 tho vast forests which at present afford us coal, the remains of beetle-like insects are discovered. Evidences of terrestrial life are alse furnished by fish-like lizards, frog-like reptiles, and a Unking 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 of high organization. At the same time, the general character of the forms of life contemporaneous with them has altered. The molluscs present greater differences, the bone-encased fishes of the Devonian age have given place to others more resembling those now existing. Insects are more varied. We have yet no evidence of true birds, but only of reptiles walking bird-like on their hind feet; none of true mammals, but only of those which produce their young in so imperfect a state that it has been well said that it is a shell-less egg that is born—it is marsupial-like animals, such as are allied to the kangaroo, which precede the true mammals. In the OoUtic, reptiles abound to such an extent,— wade through the marshes, swim on the sea, fly over the land,—that it has been termed pnr excellence the " age of reptiles." Traces of true birds also become noticeable towards the close of this epoch. But in the chalk these indications became more frequent, and here also are signs of the existence of true mammals. But with tho Tertiary epoch, while vast numbers of species which characterized the preceding ages have become extinct, others take their place—become as it were the dominant and special forms of existence. It is here that the birds whose gigantic remains form the curiosities of our museums—the Epiornis of Madagascar, the Dinornis of New Zealand—come on tho scene; it is hero that enormous mammals, as tho Megatherium and Mastodon, are first discovered. The whole of creation has been gradually assuming the aspect it presents to us now. In the Tertiary strata, we perceive how plant, mollusc, fish, bird, mammal are becoming more and more like the forms they exist in today. Myriads on myriads of individuals, nay thousands of species arise and decay; only those forms abide which are compatible with the general character of the world's advancing life—which are oue with that great scheme wu'c'1 slowly culminates in man; for
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 organism 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 oue another, yet possess distinctive features, how the forms which characterize them, widely different as some of them are, may yet bo traced back to a similar ancestry; how the lifeenergy of the world has thus fashioned for itself one language and one history, we cannot bo ius< nsiblo 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 tho 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 mto cells, cells into folia, folia into axes, axes into branch-combinations—such iu 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."*
Look again at the simple starchy mass whichi 3 tho substance of the acorn, and notico 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 tho 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 tho roots diverges from the stem. Neither in tho evolution of the whole vegetable kingdom con we perceive where the specific characters of one individual class or species begins, nor where, indeed, their infiueuco ends. Vegetable progress, like all other, is continuous, is cumulative. Myriads on myriads of individuals have lived and died, nud 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, tho summer its maturity, tho autumn its decay. So has the vegetation of tho 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 tho 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.
(To be concludeil next week.)
(Continued from page 468.)
O Q A Another kind of gasometer. The vessel e£(J\J, A, has permanently secured within it a central tube a, which slides on a fixed tube b in the centre of the tank.
281. Wet gas meter. The outer case is stationary, and filled with water up to above the centre. Tho inner revolving drum ■ is divided into four compartments, B B, with inlets around the central pipe u, which introduces tho 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 tho drum iu the direction of the arrow shown near its periphery, displacing the water from them. As the 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 through the metro is registered.
282. Gas regulator (Power's Patent), for equalizing the supply of gas to all burners of a building or appartment, 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, aud connected by a lever, (/, with on inverted cup, H, the lower edges of which, as well as those of valve, dip into channels containing quicksilver. There is no escape of gas around the cup H, but
• " Principles of Biology," vol. ii., p 21i.
there are notches, b, in the valve to permit the gas to pass over the surface of the quicksilver. As the pressure of the gas increases, it acts upon the inner surface of cup H, which is larger than valve, and the cup is therehy raised, causing a depression of the valve into the quicksilver, and contracting the opening notches b, and diminishing the quantity of gas passing through. As the pressure diminishes an opposite result is produced. The outlet to burners is at F.
'283. Dry gas meter. Consists of two bellows-like chambers, A A1, which are alternately tilled with gas and discharged through a valve B, something like the slide valve of a steam engine, worked by the chambers A A1. The capacity of the chambers being known, and the number of times they are filled being registered by dill-work, the quantity of gas passing through the metre is iuilicated on the dials.
28-1. A spiral wound round a cylinder to convert the motion of the wind or a stream of water into rotary motion.
285. Common windmill, illustrating the production of circular motion by the direct action of the wind upon the oblique soils.
28f>. Plan of a vertical windmill. The sails are so pivoted as to present their edges iu retunung towards the wind, but to present their faces to the action of the wind, the direction of which is supposed to be as indicated by the arrow.
287. Common paddle-wheel for propelling vessels; the revolution of the wheel causes the buckets to press backward against the water and so produce the forward movement of the vessel.
288. Screw propeller. The blades are sections of a screw-thread, and their revolution in the water has the same effect as the working of a screw in a nut, producing motion in the direction of the axis and so propelling the vessel.
289. Vertical bucket paddle-wheel. The buckets, a n, are pivoted into the arms, b b, at equal distances from the shaft. To the pivots are attached cranks, c c, which are pivoted at their ends to the arms of a ring, d, which is fitted loosely to a stationary excentric, e. The revolution of the arms and buckets with the shaft causes the ring, il, also to rotate upon the excentric, and the action of this ring on the cranks keeps the buckets always upright, so that they enter the water and leave it edgewise without resistance or lift, and while in the water are in the most effective position for propulsion.
290. Ordinary steering apparatus. Plan view. On the shaft of the handle-wheel there is a barrel on which is wound a rope which passes round the guide-pulleys and has its opposite ends attached to the "tiller" or lever on the top of the rudder; by turning the wheel, one end of the rope is wound on and the other let off, and the tiller is moved iu one or the other direction, according to the direction in which the wheel is turned.
291. Capstan. The cable or rope wound on the barrel of the capstan is hauled in by turning the capstan on its axis by means of hand-spikes or bars inserted into holes in the head. The capstan is pre
vented from turning back by a pawl attached to its lower part and working in a circular ratchet on the base.
292. Boat-detaching hook (Brown & Level's). The upright standard is secured to the boat, and the tongue hinged to its upper end enters an eye in the level which works on a fulcrum at the middle of the standard. A similar apparatus is applied at each end of the boat. The hooks of the tackles book into the tongues, which are secure until it is desired to detach the boat, when a rope attached to the lower end of each lever is pulled in such a direction as to slip the eye at the upper end of the lever from off the tongue, which being then liberated slips out of the hook of the tackle and detaches the boat.
293. "Lewis,'' for lifting stone in building. It is composed of a central taper pin or wedge, with two wedge-like packing-pieces arranged one on each side of it. The three pieees are inserted together in a hole drilled into the stone, and when the central wedge is hoisted upon it wedges the packing-pieces out so tightly against the sides ef the hole as to enable the stone to be lifted.
294. Tongs for lifting stones, &c. The pull on the shackle which connects the two links causes the latter so to act on the upper anus of the tongs as to make their points press themselves against or into the stone. The greater the weight the harder the tongs bite.
295. Entwistle's patent gearing. Bevel-gear, A, is fixed. B, gearing with A, is fitted to rotate on stud, E, secured to shaft, D, and it also gears with bevel-gear, C, loose, on the shaft, D. On rotary motion being given to shaft, D, the gear, E, revolves around A, and also rotates upon its own axis, and so acts upon C in two ways, namely, by its rotation on its own axis and by its revolution around A. With three gears of equal size, the gear, C, makes two revolutions for every one of the shaft, D. This velocity of revolution may, however, be varied by changing the relative sizes of the gears. C is represented with an attached drum, C. This gearing may be used for steering apparatus, driving screw-propellers, ifcc. By applying power to C, action may be reversed, and a slow motion of D obtained.
296. Drawing and twisting in spinning cotton, wool, &c. The front drawing-rolls, B, rotate faster than the back ones, A, and so produce a draught, and draw oat the fibres of the sliver or roving passing between them. Roving passes from the front drawing-rolls to throstle, which, by its rotation around the bobbin, twists and winds the yarn on the bobbin.
297. Fan-blower. The casing has circular openings in its sides through which, by the revolution of the shaft and attached fan-blade, air is drawn in at the centre of the casing, to he forced out under pressure through the spout.
298. Siphon pressure gauge. Lower part of bent tube contains mercury. The leg of the tube, against which the scale is marked, is open at top, the other
IN our last article on this subjectJ£e»cA-^*^
B the amount of stiffness given to them, either by V creasing the sectional area of metal in them, or adopting a form of section adapted to ensure the s quisite rigidity. It will be at once apparent that >«.-■ Rreater the number of the crossings of the bars 'la less becomes the actual length of any unsupported bar. Every intersection of two bars, supifcasing it to occur at the middle of their respective u grths, virtually reduces those lengths one-half, ad the stiffness of the bars is thus nearly doubled, Jr -while the original strain remains the same, the •iiilfiiiy of the bars to deflect is very considerably diminished. This was one of the causes that ""peedily proved how deficient the Warren system •«s iii those points when girders of large span .' 'ere proposed to be constructed on that principle. |> t was soon discovered that it was absolutely impossible to construct a deep girder with only one Heries of triangles. The amount of material that it vss necessary to introduce in order to afford the proper degree of stiffness to the bars was very much In e xcess of that wliich would be required in a solid»ided or plate girder. It must be borne in mind t- Viat the superior economy of the open or lattice It ype of girder over that of the plate system rests in the web, and in the web alone. The flanges or I 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
which of them act as struts and which as ties. When we proceed to analyze the strains upon a bent crone, 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 extremity of the crane are subject to compressive 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 fonnuhe are no longer applicable, and those that would theoretically apply to each particular case in question are so exceedingly troublesome, complicated, and uncertain, as to be practically useless. It is not too much to assert that to attempt to employ algebraical or mathematical equations and formulie 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.
A reference to Fig. 2 will show that a plain bar section will not answer for the compressive bars in the web of a bent crane. This is owing to the fact that a plain rectangular bar has little or no lateral stiffness. It is true that when occupying the position of one of the diagonals in the web of a girder designed on the lattice principle, it is stiffened to some extent by the intersections with
the other bars. But this is not sufficient, and it becomes necessary to adopt a form of section that by virtue of its own shape shall possess some degree of inherent stiffness and rigidity. Independently of this reason there is another. It is that although the intersections of the bars do contribute to the stiffening of the web of the girder, yet they are not supposed to actually prevent the bar from deflecting. There is little doubt that they in reality do so, but it must not be taken into account when proportioning the bars, because it is always assumed that there is no extra strain brought upon the respective bars by their being riveted or bolted to one another. It is at the some time manifest that if they were prevented from deflecting, in consequence of the points of intersection, there would be a considerable transverse strain iuduced upon them. This strain, which would increase with the length of the bar, would altogether vitiate the whole principles of girder construction, as we have already frequently explained in our columns.
The form selected for the compression bars in Fig. 2 is that of angle iron, but there are several other forms equally suitable. Of these, tee or channel iron is to be preferred, hut they all j-icld to angle iron in simplicity and facility for attachment. Moreover, the last description of section is that most readily procurable in the market. It can always be obtained of the usual scantlings at a very moderate price per ton, whereas some of the other sections are only to be obtained by special order, thus entailing a long delay, and sometimes are not to be had at all. There is no greater mistake made than to design a structure with a quantity of impossible-shaped material in it. As a rule, always select those forms, sections, and sizes of iron that are the most readily obtained, and at the most moderate cost. It is not only the shape of the iron that is of importance, but the dimensions. When bars beyond a certain length in one piece are wanted, or plates containing more than a certain maximum superficial area, there is an extra price per ton charged. Thus, a narrow plate of about 12in. broad can lie procured at the ordinary market prices in a considerably longer Bingle length than 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 onr 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 tho 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 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.
In large examples, the opposite diagonals are nnited, not merely by horizontal pieces of bar, but 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,
Wo must reserve for the next article on the subject the investigations into the strains upon these braced specimens of construction.—Building Xcics.
USE OF ELECTRICITY IN fcAUTERIZATION.—The old method of cauterization by lire is to be replaced by the electro-thermic or gRlvane-oaustic 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 supprein it, to render it intermittent o'r continued, to direct it into deep cavities, and to destroy all the tissues by contact. It is said that the wounds produced by electricity are less liable to contagion and miasmatic infections than those cansed by sharp instruments. The apparatus csn be made of any desired shape so as to bo applicable to all parts of tho body, and it is known that important cures have been effected bv the introduction of platinum wires and the cauterization by the battery nf parts ol tho body inacoessible in any other way. Electricity has already been tried in cases of bad tumors, in amputations, in excisions of cancers, in destruction of wens, fi>r opening cysts, for removing internal tumors, upon wounds by fire, and in numerous other cases. A recent article in Coimo* claims for it the following advantages: The electro-thermic cautery suppresses all pain after the operation; avoids loss of blood; prevents the retention and alteration of the liquids; avoids all putrid and purulent infections; facilitates the organic reconstruction and healing of the parts; affords a method unhersally applicable, strong or weak, continuous or intermittent; capable of sloughing the tissues, of (.urbanizing them, of destroying them, of converting thcn, 'nto Ba8' "nu must oe regarded as <>ne of the most important contributions to modern surgory."
THE FORECASTING OF STOKMS.*
IT cannot be denied, that the complicated and constantly varying phenomena of that fickle entity wliich we denominate the weather form a problem which in the nature of things must be extremely difficult of solution; and it is hardly probable that any man will ever be able in this field of inquiry to reach the same satisfactory results that have rewarded the labours of the astronomer. It is a source of legitimate pride to Americans, however, that in two important departments of meteorological investigation citizens of this country hold the first rank. To Dr. Franklin belongs the honour of discovering and elucidating the principles of electricity, and of demonstrating the influence of that subtle force upon the earth and its atmosphere; and it was Bedfield who, something like a century later, deduced from his own careful observations of storms upon our Atlantic coast the important generalization that there is a class of great storms which originate near the eqnator, in the region of the West Indies, and rapidly advance, according to a fixed law, with a simultaneously gyratory and progressive motion, upon a well-defined curved axis towards the north pole. These storms vary greatly in intensity and in breadth—sometimes being confined to a narrow belt upon or a little way off from the coast, and again extending over a wide expanse of land and sea; but that they uniformly follow the same general course indicated by Bedfield has been abundantly established by a great number of subsequent observations. It is not designed here to enter into an elucidation of this important law, but attention is called to it as marking one of the few real and tangible and practical achievements in the field of meteorological science. Its discovery and announcement stimulated investigators both here and in the Old World to renewed energy in thenefforts to unravel the mysteries of atmospheric phenomena. The subject of storms, both ocean and inland, was especially studied with quickened zeal and enthusiasm: and in due course of time an attempt was made abroad—first in England, then in France, and afterwards in other continental conntries—to utilize tho knowledge gained thereby in the interests of commerce, which, ever since it has existed, has been subjected to constant peril and loss from the effects of storms. The prevailing courses of the most destructive storms in various localities having been definitely ascertained, measures have been taken to give warning to exposed points of their approach, by means of the telegraph. This intelligence being promptly communicated Inpreconcerted signals to all vessels passing within sight of the shore or lying at anchor in harbour or roadstead, such vessels are enabled to take all necessary precautions against disaster before the storm shall burst upon them ; and immense damage to shipping has thus in very many instances been avoided.
Notwithstanding the salutary operation of this system abroad, however, and notwithstanding the peril from storms to wliich 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 resolution providing "for taking meteorological observations at the military stations and other points in tho 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:—
"Be it resolved by the Senate and House of Representatives of the fhiited Stntrx 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, and at other points in the States and Territories of the United States, and for giving notice on the northern lakes and on the sea-coast, by magnetic telegraph and marine signals, of the approach and force of storms."
This resolution was promptly passed by both houses of Congress, and on the 9th of February, 1870, became a law by the approval of the President. By General Orders No. 29 from the head-quarters of the army, dated March 15, 1870, the chief signal officer of the army, Brevet Brigadier-General A. J. Myer, is charged, subject to the direction of the Secretary of War, with the execution of the provisions of this enactment, and all commanding officers are enjoined to afford every facility for the successful prosecution of the undertaking; while scientific establishments, commercial associations, and others, are requested to aid, by their co-operation, in the accomplishment of the work.
Professor J. A. Lapham, of Milwaukee, impressed by the frightful aggregate of a single year's disasters to vessels on the great lakes—amounting for tho year 1869 to the immense number of 1,914, wiffc an estimated damage to property of over four millions
* Extracted from an article by L. A. Roberts in the Wettern Monthly.
of dollars—was perhaps the flint to suggest some action by Government for inaugurating such a system of storm-reporting as, through the efforts oí 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 ñnal fury upon the ocean and its navigators.
Nor must we overlook the damage often worked on land, as well as upon the water, by these latter 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 fo 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 forgot 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 RB 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
down, crushing the horses and burying himself to the middle in its débris—and there he stands, upright, stark dead in an instant! A little farther down the street an unfinished frame building goes down even before the workmen upon it can reach the ground, and three men are crushed in the mass of timbers and escape death by a miracle.
All this, and vastly more, in one little village; and a dozen villages are in the track of the monster. Ay, a monster he is, and almost insatiable, but not quite; for right in his course stands a little countryhouse, the inmates of which, looking westward, hear his roar and see him come crashing through a belt of woods a quarter of a mile away. They make such hasty preparations as they can for the impending catastrophe; but, to their utter astonishment, they find in [a minute or so that the storm has passed them by unharmed and is tearing through the woods to the east of them. This characteristic of these tempests has been often observed. While in general they move upon the ground, sweeping it clean as they go, occasionally they rise above it, and again descend—bounding, as it were, like an india-rubber ball that has received a superior ground stroke from the champion batter of a " firstnine."
(To be concluded next week.)
CEMENTS AND HOW TO USE THEM.
GREAT deal has been written concerning different cements, and indeed our periodicals ore 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 </iü vire 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 hflfto» it has time to effect a thorough adhesion. Tht «jSLW*"*'*«-' eminently true in regard to cements Цщ лгс used in ^j, fuse(¡ state, such as mixtures of n-rjj slieU«C an<\jê чйпТгдт materials. These matters iii uot """A'Cirfe to any substance unless the lattcj ¡,&9 bw--¿í:n heated to nearly or quite the fusing р<щ ef t*; he cement used. This fact was quite families ' ..JHhosc who used sealing-wax in old days. When the seal was used rapidly, so as to become heated, the sealing-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 adhering 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.
Unless this adhering layer of air is displaced, the cement cannot adhere to the surface to which it is applied simply because it cannot come into contact with it. The most efficient agent in displacing this air is heat. Metals warmed toa pointa little above 200,become instantly and completely wet when immersed in water. Hence for cements that are used in a fused condition, heat is the most efficient means of bringing them in contact with the surfaces to which they are to be applied. In the case of glue the adhesion is best attained by moderate pressure and friction. Another very important point is to see as little cement as possible. When the surfaces are separated by a large mass of cement we have to depend upon the strength of the cement itself, and not upon its adhesion to the surfaces which it is used to join ; and, in general, cements are comparatively brittle.
CARBON PRINTING ON ENAMEL TABLETS AND PORCELAIN SURFACES.
THE production of a carbon opalotype is probably one of the easiest feats in photographic printing of any kind. Not so, however, is the printing on a rounded or convex surface, such as an enamel tablet of the usual kind. This is attended with some difficulties, but they are not of such I nature as to prove insurmountable; moreover, the extreme beauty of a picture on a convex or lunette surface is such as to justify the expenditure of almost any moderate amount of labour in order to overcome them successfully. To do this some modifications in the process are requisite. The first and most important one is to procure a tissue much more flexible than any hitherto in use; and by flexibility we do not here allude to the gelatined sensitive film itself, but to the paper which is employed as a means of support for that gelatine. The commercial tissue that we have hitherto been, using in our experiments has a hard, stiff paper as its foundation, and if tried for the purpose here proposed will require more than ordinary care to ensure a successful result.
When trying some experiments with a view to the writing of the present article, we made some tissue on a basis of thin and imperfectly-sized paper. Whereas the ordinary commercial tissue was so hard and brittle as to admit of its being broken across, this, although when dry still stiff and unyielding, was devoid of brittleness, and after a brief soaking in water became quite limp and flaccid. This last is one of the main conditions of success in carrying out a carbon printing process upon a rounded surface.
With these explanatory observations we now proceed to give such instructions as will enable any careful experimentalist to succeed.
First of all, make a reverse cast from the face of the enamel tablet. This may be done either in gutta-percha or plaster of Paris. The 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 tablet on which it is intended to make the picture, and, МУ means of a penknife or a pair of scissors, cut the pigmented paper to the exact size. Now expose this in the printing frame under the negative, and observe that in the subsequent operations it vignette can be more easily manipulated than if the picture be printed up to the margin. The reason for this has already been stated. The pigmented paper, on being removed from the printing-frame, is placed in cold water, and in the course of a minute or two becomes quite pliable. It is now laid carefully down upon the enamelled tablet and covered with a piece of blotting-paper, which ought also to be cut to the same size.
The mould of gutta-percha or plaster of which we have already spoken is now carefully laid down upon the top of the paper, which then inclines to the exact form of the enamel convex surface, and is also retained in close contact with it. With a very pliable tissue and a very slightly-rounded surface, contact may be made by means of the squeegee, but with enamels of the best form this cannot be done. In this case, the means we have here described or some method analogous must be had recourse to.
When the paper bas become partially dry the method of development is precisely similar to that recommended in the former article on transparency printing—viz., immerse the tablet first in cold water for a short time, then in water of nearly the temperature of 100° Fahr., and, after removing tho paper, continue to allow the hot water to flow backwards and forwards over the surface until every detail be perfectly visible. Now, before the picture is allowed to dry, immerse in a weak solution of alum, and finally rinse in water and dry. The resulting picture will be quite equal in respect of beauty to anything that can be done by burning-in. and at the same time it will be quite as durable, 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 to coagulate this varnish. We have tried other varnishes—among them amber and chloroform— with good effect.
No person except an expert can distinguish ■etween a picture produced by the method described mil one that has been bnmt-in in a muffle.—The 'British Journal of Photography.
iXPEEIMENTS ON THE RESISTANCE OF IRON AND STEEL.*
UNDER this title the author publishes the results of experiments, 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 :—
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 proportional to the disturbance of cohesion. The absolute magnitude of the limiting strains is effective only as it diminishes the difference attendant upon increased strain, which difference causes rupture.
The tensions and compressions affecting the same libre 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, vibrations may occur within the following limits of safety for each (German) square '■ section :—
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, Ac.
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 than 800 ctr. It often reaches 900 to 1,000 ctr.; and with good steel a further increase is possible.
Those parts of boilers which are not exposed to the fire, if of cylindrical form, are subject to but slight vibrations, which are caused by the variation of the tension of the steam. Hence a greater strain is allowable than has been generally applied; but in the parts exposed to the fire, not only the waste by burning, but also the motion of the molecules due to the varying temperature, must be considered. It is not improbable that the continued movement of molecules, caused by heat, acts to destroy cohesion, just as vibrations caused by other forces act.
The effect of strain is entirely different, if it is constant and static, from the effect when it is variable and productive of vibrations. It is also important to consider whether a structure is intended to serve a purpose for a limited period, or to stand for an indefinite time. It follows that like factors of safety do not suit all constructions. In every case two factors are necessary; one, which determines the ratio of absolute breaking strength; another, which fixes the ratio to the vibration that induces rupture by indefinite repetition.
The coefficient of safety should be taken large enough in comparison with the absolute breaking strain, that it may compensate for want of homogeneity of mat trial. For this the factor 2 is sufficient. Material requiring a larger coefficient in this respect should be rejected. The limits of elasticity have not thus far been considered, and it must be left to the judgment to determine between what limits continuous deflection is allowable. A single loading, preventing further deflection, can do no harm, if it does not approach the breaking
weight. In large structures it is a general rule that the limit of elasticity should not be passed.
As a coefficient of safety for repeated vibration,
is in all cases sufficient, and in many cases is higher than necessary.
i\.s a result of his experiments, the author gives the following table of inch-strains for permanent structures:—
strained in both directions 80ctr.
„ „ one direction, total strain 180ctr.
of which not more than 150 etc. should be due to the variable load. If the constant strain is less than 30 ctr. the permissible total strain must be proportionally less.
For unbammered cast steel,
Strained in both directions 120 ctr.
„ ,, one direction, greatest total
strain 330 ctr.
of which not more than 220 ctr. should be due to the passing load. The constants apply to pieces of uniform section.
Experiments with spring-steel show that carsprings should not be loaded to three-fourths of the breaking resistance, if the play of the spring is small in proportion to the entire deflection. With a constant strain of 900 ctr. a play of between 900 to 1,200 ctr. is allowed.
paper or glass is fixed upon the upper end of the tube. Heat being applied to the bulb, drives out the air through the meronry, the latter, as suou 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 bo sealed hermeti cally. 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 manipulations 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, sufficiently accurate indications for the regulation of the temperature of apartments, and for other ordinary purposes.—Scientific American.
Translated from Polyleehnitehei Centralblatt.
HOW MERCURIAL THERMOMETERS ARE MADE.
A MERCURIAL thermometer is a very simple J\. instrument. A small glass tube, with a bulb at one end, containing mercury, and a graduated scale, constitute all that is essential to it; yet iu this, as in many other cases, simplicity begets difficulty. To make this simple combination perform 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 means of eliminating the errors which would arise from this source be adopted, nothing like accuracy can be expected in the indications of the instrument. As the character of the bore cannot be altered, the desired result must be obtained in another way.
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 bogs, to which pressure is applied, and regulated by Bcrews. 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.
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 wires being employed to aid the eye of the operator in performing the operation with exactness. By means of the rubber bags the mercury is again forced along until the end of the column, where the first mark is made, is brought under the microscope cross wise, placed at the other end, and so on throughout the entire length intended to be graduated. The varying lengths of the column, which are accurately measured in the different positions, are recorded, and indicate the variations in the calibre of the tubes. A permanent mark is made at the end, as at the beginning of the calibration.
It will be seen, that if the spaces successively occupied by the mercury be divided into an equal number of equal parts, any one of these parts will indicate a corresponding increase of volume, although the bore of the tube may vary in its diameter.
The required dimensions of the bulb are found, approximately, by weighing it measured length of the mercurial column, and computing the capacity of the bulb from the known expansion of mercury and its specific gravity.
The bulb may be formed upon the tube previous to the calibration, or afterwards attached. In the former case, however, the thermometers have their scale divided after the determination of the freezing and boiling points, and no tubes can be used except such as are found to be approximately perfect. In the latter case, the arbitrary scale, as marked from the calibration, may be reduced after the determination of the freezing and boiling points into the Fahrenheit scale, by the application of a simple algebraic formula.
The freezing point is determined by placing the bulb in finely pounded ice, from which the water is drained away as it melts. The boiling point is obtained by placing the bulb in steam having the same elasticity as the atmosphere—it peculiar apparatus, devised by Reguault, being generally employed for the purpose. In puling in the mercury, a small reservoir of
SOCIETY OF ARTS, EDINBURGH.
AT the fourth monthly meeting of this society, Mr. D. W. Kemp delivered the first of a series of lectures on "Experimental Chemistry." In introducing 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 "Correspoudenoe" columns in the ever-increasingly-valuable English Mechanic, and held it as a matter to be deplored 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 truth 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.
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 had sub-divided those into upwards of sixty simple bodies, and, what is of more practical importance, had 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 tho difference between mechanical and chemical elements and compounds. Daring the re- mainder of the lecture he confined himself solely to the gas oxygen, and by several very interesting and beau, tiful 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."
In consequence of the resignation of the secretary, Mr. C. E. Gordon was appointed to that past pro tern.
Report of Obtervatiam made by the Members during the period from July 7th to August 6tfc, 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 tho two hemispheres, those to the south of tho 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 normal class, while the latter consisted chiefly of solitary specks, without penumbra?, and clusters of minute black punctures, which frequently assumed very grotesque configurations. A striking feature of the large groups observed during the early part of the month was an evident tendency either to close up, or to become dissociated upon reaching a certain position on the disc about halfway between the E limb and the centre. On the 25th one of the largest groups observed this year appeared at the E limb. On the 28th it measured nearly 5' in length, and consisted of a large preceding spot 1' 10' in diameter, followed by a straggling train of "wispy" penumbra-, enclosing several small spots. This group dwindled away very rapidly after the 28th. Another large spot, about 50' in diameter, was observed from July 13th to 25th. Fresh groups observed in tho sun's N. hemisphere
during Julv = 9
Ditto ditto S. ditto = 12
Maximum number of groups on (Use 12 (July 30,5h.
50m.) Minimum ditto 4 (July 28, 5h. 50m.)
Mr. Albert P. Holden, of London, says:—" I observed a very interesting spot on June 21, at 7 a.m. -,