matter of small-pox and scarlet fever is particularly persistent. Clothes which had belonged to some one suffering from small-pox, and been laid by for months, have passed on the complaint to those who have had the misfortune to handle them. The poison of scarlatina is most difficult to eradicate, chiefly from the desquamation or peeling off of the skin, which occurs when the malady is passing away, and which is the chief medium for the dissemination of the contagious matter. The skin or cuticle comes off in very fine powder, which is extremely light, and penetrates into every corner of the room which dust can reach, accumulating on the cornice of the door, on the shelves of bookcases, or projecting parts of picture frames. The clothes which the sick man has worn are a frequent medium of contagion; it has been noticed that they have been sent for miles to people who were quite ignorant of the fact that they came from an infected place, and yet have communicated the contagion. Woollen clothes retain the infectious material much more than cotton, for the obvious reason that wool, from its structure, is much more likely to absorb the poison than cotton. Black clothing also retains the contagious material for a longer time than white; this fact is quite unexplained. It was first noticed at the military hospitals in Vienna, where it was found that when a soldier with a white uniform had recovered from an infectious disease, and was sent back to the barracks, fewer admissions into the hospital were made of his fellow-soldiers, suffering from the same disease, than when the patient's uniform had been of a dark colour.

The bed clothes and bedding, from the wool and hair which they contain, offer a large surface for the reception and retention of the contagious material. The carpets and curtains are frequently sources of contagion, because seldom disturbed. Drinking-water also conveys the infection; the emanations from the sick man, the water in which he has washed, &c., are too often thrown carelessly away, and unless properly disinfected, the contagious material may find its way into wells and cisterns, and thus spread the disease. Typhoid fever, which destroys on an average 10,000 people in the prime of life, every year in England, is almost solely propagated by the drinking water, as it is very slightly contagious to those who nurse or tend the sufferers. Dr. Snow, in his work "On the Mode of Communication of Cholera," has proved most conclusively that cholera is chiefly communicated by the drinking water, and but seldom through the ordinary means of infection. To conclude this subject, it must not be forgotten that each specific disease has its own specific germ. The poison of small-pox will not produce measles, but only small-pox; and an attack of small-pox offers no protection whatever against measles. When the contagious matter meets with an individual in a condition favourable to the production of the disease (for, like the seed, the contagious matter must be placed in a fit soil before it can germinate), the individual thus attacked does not at once show symptoms of illness, nor indeed does he know that he is going to be ill, but there is always an interval, usually many days, between the reception of the poison, and the first feeling of inalaise. This stage is called the stage of incubation, in which the disorder is latent within the patient; for there are no signs or symptoms by which it can be known that he retains within him the seeds of severe illness; he goes about his ordinary occupations, and feels quite in his usual health. This period of incubation varies in different illnesses; in small-pox and measles it is twelve or fourteen days; in scarlet fever it lasts from five to twelve days, never being less than five, or more than twelve, in duration. The knowledge of this fact may often be of practical use; if a child have been, by chance, to see another who has taken the measles or scarlet fever, the mother would know that all risk of the infection would be over in about a fortnight from the time of the visit. For this reason it is that travellers are detained so long a time in quarantine, lest any of them might be in the incubative stage of an epidemic.

never lasts, and within which it never terminates, another; suffice it to say that among all these
except by the death of the patient. The tendency changes of form, and sometimes of quality, the ele
of this stage is to end, after its specific duration, ment of quantity remains the same.
Those of our
in the complete recovery of health. In no com- readers who are mathematicians know what is
plaint is this better exemplified than in typhoid meant by variable quantities, for instance, in the
fever. Here the specific illness never lasts less equation x+y+2=A, if x, y, and z are variable and
than twenty-eight or more than thirty days; A constant, you may change a into y and into ≈, and
during this time the patient is feverish, with ay into c and into z, and in fact, perform any changes
temperature of the body often rising to 105° Fahr., you choose upon the left hand side of your equation
and is delirious and entirely without appetite. If provided that you keep their sum always constant
the patient only survive the twenty-eighth or and equal to A. It is precisely thus in the world of
thirtieth day, the fever and delirium go, the tem- energy; and the invariability of the sum of all the
perature of the body falls to the natural standard, energies of the universe forms the doctrine known
98° Fahr., and the appetite begins to return. This as the "conservation of energy." This doctrine is
illustrates what was said about the power of curing nothing else than an intelligent and scientific denial
disease, and the importance of an intimate acquain- of the chimera of perpetual motion.
tance with its natural history. Here the physician
is aware that he cannot cure, but at the same time
he knows that if he can keep his patient alive over a
certain day, the patient will recover; the only
endeavour of the physician in this case is, then,
uply to prolong life, to enable the patient to live
over the critical day, and thus by simply endeavour-
ing to prolong life, the physician often succeeds in
saving life.

In this specific stage there are two symptoms,
the specific process, and fever. In small-pox and
measles, the specific process is the rash on the skin;
in scarlatina, the rash on the skin, and the sore
throat conjoined; while in diphtheria it is the sore
throat alone, which is the specific process. This
specific process is the essence of the whole disease,
without which the disease could not exist, and the
means by which the disease is propagated. The
specific process itself is strictly local, never affect-
ing all the tissues of the body generally, but limit-
ing itself to one set of tissues, or to those analogous
to it. Thus in small-pox, the local specific process
is limited to the skin alone, except when it attacks,
in grave cases, the mucous membrane, similar in
structure to the skin, of the windpipe and air-tubes
of the lungs. In diphtheria, the mucous membranes
alone are involved, while in typhoid fever it is the
adenoid tissue, which the spleen and some other
organs largely contain, that is affected. Fever is
a constant accompaniment of the local specific
process; and by fever we simply mean that the tem-
perature of the body, as measured by the thermo-
meter, is greater than in health. The natural tem-
perature of the body is 98° Fahr., but in fever it rises
above this. The temperature of the body in health
is maintained by a constant oxidation or burning
of the tissues by the oxygen of the air, brought by
the blood from the lungs. In fever, this process of
combustion goes on more rapidly, and the tissues
are burnt away at a higher rate, and thus an eleva-
tion of temperature is produced. A great increase
in the products of combustion, which are eliminated
from the system, takes place during the fever, or
at its termination. This process of increased com-
bustion readily explains the rapid emaciation which
occurs in fevers. The great debility of the patient
depends upon the exhaustion produced by the high
temperature. According to Joule's law, every
degree of increased temperature represents a certain
amount of mechanical exertion. The Rev. Professor
Haughton says: "The work due to animal heat
would lift the body through a vertical height of
eight miles per day; and it thus appears that an
additional amount of work, equivalent to the body
lifted through one mile per day, is spent in main-
taining its temperature at fever heat. If you
could place your fever patient at the bottom of a
mine, twice the depth of the deepest mine in the
duchy of Cornwall, and compel the wretched suf-
ferer to climb its ladders into the open air, you
would subject him to less torture from muscular
exertion, than that which he undergoes at the hand
of nature, as he lies before you, helpless, tossing,
and delirious on his fever couch."

(To be concluded next week.)

THE

WHAT IS ENERGY ?*
PART III.
CONSERVATION OF ENERGY.

(Concluded from page 391).

The end of the stage of incubation is announced when the person begins to feel ill; what is called the stage of invasion has arrived, and this is the commencement of the illness properly so called; IT is, well known that certain organisms of the animal world do not confine themselves to one like the stage of incubation, this has a course of a state of being or to one order of existence, and the certain number of days, varying in each disease. most familar instance of this roving habit is In scarlet fever the invasion-stage lasts only twenty, the caterpillar, which passes first into the chrysalis four hours, and is accompanied by feverishness and state, and after that into the butterfly. This habit sore throat; in small-pox it lasts forty-eight hours, is not, however, peculiar to the organic world; for and there is also a great pain in the back, and energy delights in similar transmutations, and we the patient feels seriously ill. In measles this have just seen how the eminently silent and invisible stage lasts three days, during which the child is electrical current may occasionally be transmuted feverish, and its eyes and nose pour out a fluid, into the vivid, instantaneous, awe-inspiring flash of which scalds the skin over which it flows. In lightning. Nor is this element of change confined whooping-cough, the stage of invasion lasts nearly a to our peculiar corner of the universe, but it extends fortnight, during which time the child seems to itself to remote starry systems, in some of which have only an ordinary severe cough, without any- there is a total extinction of luminosity for a while, thing to announce its specific character. When to be succeeded by a most brilliant outburst, prethe complaint is in the stage of invasion, no drug senting all the appearance of a world on fire. or medicine is known which has the least power to stop the illness from going on further into the specific stage, which, like the two preceding stages, has a sharply defined duration, beyond which it

We shall not enter here into great detail regarding the various changes of energy from one form into

By BALFOUR STEWART, in Nature.

Recognizing the great importance of work, it was natural enough at an early stage of our knowledge that enthusiasts should endeavour to create energy or the power of doing work-that is to say, endeavour to construct a machine that should go on working for ever without needing to be supplied with fuel in any way-and accordingly, inventors became posessed with the idea that some elaborate system of machinery would, no doubt, give us this grand desideratum, and men of science have been continually annoyed with these projects, until in a moment of inspiration they conceived the doctrine of the conservation of energy.

It flows from this doctrine that a machine is merely an instrument which is supplied with energy in one form, and which converts it into another and more convenient form according to the law of the machine.

We shall now proceed to trace the progress of energy through some of its most important transformations. To begin with that one to which we have already alluded, What becomes of the energy of a falling body after it strikes the earth? This question may be varied in a great number of ways. We may ask, for instance, What becomes of the energy of a railway train when it is stopped? what becomes of the energy of a hammer after it has struck the anvil? of a cannon ball after it has struck the target? and so on.

In all these varieties we see that either percussion or friction is at work; thus it is friction that stops a railway train, and it is percussion that stops the motion of a falling stone or of a falling haminer, so that our question is in reality, what becomes of the energy of visible motion when it has been stopped by percussion or friction?

Rumford and Davy were the pioneers in replying to this important question. Rumford found that in the process of boring cannon the heat generated was sometimes so great as to boil water, and he supposed that work was changed into heat in the process of boring. Davy again melted two pieces of ice by causing them to rub against each other, and he likewise concluded that the work spent on this process had been converted into heat.

We see now why by hammering a coin on an anvil we can heat it very greatly, or why on a dark night the sparks are seen to fly out from the break-wheel which stops the motion of a railway train, or why by rubbing a metal button violently backwards and forwards against a piece of wood we can render it so hot as to scorch our hand, for in all these cases it is the energy of visible motion which is being converted into heat.

But although this was known nearly a century ago it was reserved for Joule, an English philosopher of the present day, to point out the numerical relation subsisting between that species of energy which we call visible motion and that which we call heat.

The result of his numerous and laborious experiments was, that if a pound of water be dropped from the height af 772ft. under the influence of gravity, and if the velocity which it attains be suddenly stopped and converted into heat, this heat will be sufficient to raise the whole mass 1° Fahr. in temperature.

From this he concluded that when a pound of water is heated 1° Fahr. in temperature, an amount of molecular energy enters into the water which is equivalent to 772 foot-pounds, that is to say, to 1lb. raised 772ft. high against the influence of gravity or allowed to fall 772ft. under the same influence. He found again that if a pound of water to fall twice this distance, or 1,544ft. were under gravity, the velocity, if stopped, would raise its temperature 2° Fahr., and in fact that the rise of temperature under such circumstances is proportional to the height from which the pound of water is supposed to fall. By this means an exact relation is established between heat and work. Grove was the first to point out the probability of a connection between the various species of molecular energy; and the researches of Joule, Thomson, and others, have established these relations with numerical accuracy. No better example of the correlation of the various kinds of energy can be given than what takes place in a galvanic battery. Let us suppose zinc is the metal used. Here the source of energy is the burning or chemical combination of the zinc with oxygen, &c., in order to form a salt of zinc. The source of energy is in fact much the same as when coal is burned; it is the energy produced by chemical combination. Now, as we have said, the zinc combines with the oxygen and

THE SOLAR CALORIMETER.

In adverted briefly to some experimental engines vessel. In either case the reduced molecular force lation to the sun's zenith distance, it may of course

MECHANICAL MOVEMENTS.

with the interior of the calorimeter, and connected viated in the solar calorimeter, while the loss caused with an air pump for exhausting the same. A cylin- by radiation from the blackened surface of the drical vessel, termed heater, with curved top and bot-heater has been reduced to a mere fraction. It may tom, composed of polished silver, is secured in the be contended, however, that the loss by radiation lower part of the instrument, and provided with a of the polished heater against the interior polished conical muzzle at the top, through which a thermo- surface of the calorimeter, although minute, is yet meter is inserted from without. Within the lower part appreciable; and that some heat will be lost by of the heater is introduced a centrifugal paddle wheel, conduction at the points where the heater joins the surrounded by a cylindrical casing divided in two external vessel. Even these trifling sources of compartments by a circular diaphragm, the lower error, it will be seen presently, have been removed compartment containing four radial wings or paddles, by the new method. A force pump and capacious the diaphragm being perforated in the centre. The cistern containing water are arranged near the centrifugal paddle wheel revolves on an axle which calorimeter, a uniform temperature of 60° being passes through a stuffing box applied at the bottom kept in this cistern by the usual means of a warm of the double vessel, the rotary motion being im- and cold water supply. By appropriate hose and parted by means of a pulley secured to the lower the force pump mentioned, a constant current is end of the axle. The operation of this wheel, in- kept up through the space between the internal and tended to promote perfect circulation of the fluid external casings of the instrument; hence, every within the heater, is quite peculiar. It will be part of the latter may be brought to a uniform readily understood that by turning the wheel the temperature of 60° in a few minutes. The process centrifugal action of the fluid produced by the rota- of measuring the solar energy is conducted in the tion of the paddles will draw in water downwards following manner: The thermometer being withthrough the central perforation of the diaphragm, drawn, the heater is charged with distilled water and force the same into the annular space round of a temperature of about 45°, after which the the casing of the wheel; thus an upward current thermometer is again inserted. The table supportwill be kept up through this annular space uniform ing the instruments should now be turned towards on all sides. This current, after reaching the top the sun and the paddle wheel put in motion. The of the heater, will then return, first entering the indication of the thermometer must then be watched, open end of the casing of the wheel, and ultimately and the time accurately noted when the mercurial the central perforation of diaphragm. I have been column marks 50° on the scale, the observation thus particular in describing this system of promot- continuing until the thermometer marks 70°, at ing uniform circulation within the heater because a which point the time is again accurately noted. The proper proportion of the actual mean temperature experiment being then concluded, the table should of the water contained in the same is the all impor- be turned away from the sun. It scarcely needs tant condition on which depends the accuracy of the explanation, that during the elevation of the temdetermination of the number of units of heat deve-perature of the water from 50° to 60° the instrument loped. It only remains to be pointed out that the radiates towards the heater, and that while the temlens, which is so proportioned as to admit a sun perature rises from 60° to 70°, the heater radiates

beam of 52 square inches of section, is placed at

such a distance from the heater that when the concentrated rays reach the upper end (painted with lamp-black) they are confined to an area of 3-25 square inches, precisely 1-16th of the sectional area of the sunbeam which enters the lens.

It will be obvious that the concentration of the radiant heat on an area of only one-sixteenth of that of the section of the sunbeam, removes a very difficult disturbing element from the investigationviz., the great amount of heat radiated by the blackened surface of the heater, which, in the pyrheliometer, is sixteen times greater than in the solar calorimeter. But this is not all, while the sixteen times more extensive blackened surface of the former is exposed to currents of air, the disturbing effects of which can neither be controlled nor computed, error arising from convection is wholly removed from the latter, because the reduced blackened surface of the heater receives the concentrated radiant heat within a vacuum. The loss of heat at the bottom and sides of Pouillet's instrument, caused by convection and currents of air, is likewise wholly removed in the solar calorimeter by the expedient of operating within a vacuum. It will be seen, therefore, that the loss of heat by convection and currents of air has been wholly ob

towards the instrument. In each case the amount

of heat radiated, that is, the gain and the loss, is
almost inappreciable, since both the heater and the
surrounding internal vessel are composed of polished
silver. The amount of gain and loss of heat by
conduction at the points where the heater joins the
surrounding vessel, if appreciable, evidently balance
each other in the same manner as the gain and loss
by radiation.

The weight of distilled water at 60° contained in
the heater, and the weight and specific heat of the
materials which compose its parts, being ascertained,
the number of units of heat necessary to elevate
the whole 20° may be readily calculated. To this
must be added the percentage of calorific energy
lost during the passage of the sun's rays through
the lens. The sun will represent a permanent co-
efficient for each particular instrument which may
ever afterwards be employed to determine the
dynamic energy of the sun's radiant heat. Obvi-
ously the indication will be equally correct during
the winter solstice in a northern latitude with the
mercurial column at zero as during the summer
solstice within the tropics, when the thermometer
marks 100° in the shade.

It must not be supposed that the same difficulty presents itself in ascertaining the loss of calorific

energy of the rays of heat as that involved in a determination of the retardation which rays of light suffer during their passage through a lens. In order to determine the former we have only to compare the units of heat developed by the direct action of a sunbeam of a given section, with the number of units developed by another sunbeam of equal section during an equal interval and at the same time, acting through the lens, the retarding influence of which we desire to ascertain. I have constructed an instrument for this purpose by means of which the diminution of the calorific energy of the sun's radiant heat can be accurately measured for all lenses not exceeding 8in. diameter. This instrument will be delineated and explained at the proper time.

Referring to the experiments which have been made with the solar calorimeter, it is specially worthy of notice that the sun's energy, as shown by this unerring mode of measuring the force actually transferred to the surface of the earth, is never regular. The force of the radiant heat (call it molecular action) indicated by the increment of the temperature of the fluid in the heater of the instrument, is continually oscillating. At first I attributed this circumstance to invisible masses of light vapour passing through the atmosphere. More recent observations induce me to think that want of constancy in the evolution of the heat at the source may possibly be the true cause.-Engineering.

New York, June 21.

MECHANICAL MOVEMENTS.

(Continued from page 392.)

224. piston engine. The cylinder," A, of

Root's double-reciprocating or square

this engine is of oblong square form and contains two pistons, B and C, the former working horizontally, and the latter working vertically within it; the piston, C, is connected with the wrist, a, of the crank on the main shaft, b. The ports for the admission of steam are shown black. The two pistons produce the rotation of the crank without dead points.

225. One of the many forms of rotary engine. A is the cylinder, having the shaft, B, passing centrally through it. The piston, C, is simply an excentric fast on the shaft and working in contact with the cylinder at one point. The induction and eduction of steam take place as indicated by arrows, and the pressure of the steam on one side of the piston produces its rotation and that of the shaft. The sliding abutment, D, between the induction and eduction ports moves out of the way of the piston to let it pass.

226. Another form of rotary engine, in which there are two stationary abutments, D, D, within the cylinder, and the two pistons, A, A, in order to enable them to pass the abutments, are made to slide radially in grooves in the hub, C, of the main shaft, B. The steam acts on both pistons at once,

The tains.

to produce the rotation of the hub and shaft.
induction and eduction are indicated by arrows.
227. Another rotary engine, in which the shaft,
B, works in fixed bearings excentric to the cylinder.
The pistons, A, A, are fitted to slide in and out from
grooves in the hub, C, which is concentric with the
shaft, but they are always radial to the cylinder,
being kept so by rings (shown dotted) fitting to hubs
on the cylinder-heads. The pistons slide through
rolling packings, a, a, in the hub, C.

228. The india-rubber rotary engine, in which the cylinder has a flexible lining, E, of india-rubber, and rollers, A, A, are substituted for pistons, said rollers being attached to arms radiating from the main shaft, B. The steam acting between the indiarubber and the surrounding rigid portion of the cylinder presses the india-rubber against the rollers, and causes them to revolve around the cylinder and turn the shaft.

229. Holly's patent double-elliptical rotary engine. The two elliptical pistons geared together are operated upon by the steam entering between them, in such manner as to produce their rotary motion in opposite directions.

These rotary engines can all be converted into pumps.

230. Overshot water-wheel. 231.

Undershot water-wheel. 232. Breast-wheel. This holds an intermediate place between overshot and undershot wheels; has float-boards like the former, but the cavities between are converted into buckets by moving in a channel adapted to circumference and width, and into which water enters nearly at the level of axle.

233. Horizontal overshot water-wheel. 234. A plan view of the Fourneyron turbine water-wheel. In the centre are a number of fixed curved shutes or guides, A, which direct the water against the buckets of the outer wheel, B, which revolves, and the water discharges at the

circumference.

"

are ar

236. Jonval turbine. The "shutes" ranged on the outside of a drum, radial to a common centre and stationary within the trunk or casing, b. The wheel, c, is made in nearly the same way; the buckets exceed in number those of the shutes, and are set at a slight tangent instead of radially, and the curve generally used is that of the cycloid or parabola.

237. Volute wheel, having radial vanes, a, against which the water impinges and carries the wheel around. The scroll or volute casing, b, confines the water in such a manner that it acts against the vanes all around the wheel. By the addition of the inclined buckets, c, c, at the bottom, the water is made to act with additional force as it escapes through the openings of said buckets.

238. Barker's or reaction mill. Rotary motion of central hollow shaft is obtained by the reaction of the water escaping at the ends of its arms, rotation being in a direction the reverse of the

escape.

the

The western range rises to a considerable
altitude on the west border of Epigenes, and is
continued to a high mountain at the west end of a
fine walled plain just west of the crater Anaxagoras.
This plain is surrounded by high mountains, and is
by far the grandest and most imposing object in
this lunar landscape. It remained unnamed until
the late Dr. Lee suggested the designation “Gold-
schmidt" as suitable for it. The eastern division
of this region-which, as before stated, consists of
a depressed surface-is not much raised above the
surface of the Mare Frigoris on the south. The
N.E. boundary forms a separation between two
levels, as if a "fault) had occured in the line
between Fontenelle and Epigenes. The lower level,
which has upon it two short mountain arms stretch-
ing outwards from the N.E. boundary of the de-
pressed surface, extends towards Anaxagoras, and
is generally smooth. There is in its neighbourhood
a well-marked crater forming a triangle with the
N.E. angle of the depressed surface east of the
rugged land and Fontenelle. Between this crater
and Fontenelle an imperfect elliptical depression
exists, and another may be noticed to the N.E. of
this. Between the craters Timeus, Fontenelle
and Anaxagoras, the observer will find three very'
distinctly marked and individualized formations,
viz., the rugged land west of the mountain chain
passing through the east border of Epigenes; the
depressed surface on the east of the same moun-
tain chain (the interior of this depressed surface
contains several interesting objects); the third
formation is the depressed surface extending
towards Anaxagoras. To trace out these features,
to observe during the progress of the illumination
of the northern parts of the Moon's disc the changes
in aspect which they undergo as the Sun rises
higher above them, and as that hitherto unex-
plained and mysterious metamorphosis, which so
gradually creeps over the surface, obliterating some
objects and bringing out others not seen before,
passes through its various phases, together with
the gradual streaking of the landscape with the
rays from Anaxagoras, form a pleasing and instruc.
tive occupation with the telescope while the Moon
is passing from her first quarter to full; and to
those students who prolong their watchings to
'early dawn" the formations seen under the reverse
light are full of interest.

CONSTRUCTIVE HOROLOGY.* Tscience which has of late years received so comHERE is probably no branch of mechanical paratively small a share of study or made so little progress in this country as horology.

To advocate the sudden adoption of such reforms as would to any great extent alter the character of system of hand-finishing by the piece, would not be the article produced, or revolutionize the present wise, but without going to this length there is room for vast improvement and much economy to be At present every

of every wheel, barrel, and staff hole, also the poition of every screw, stud, dial-foot, &c., and the outline of every bar and cock should be defined, which would, if generally adopted, admit of every separate part of the complete watch being a ready-marke finished article, including balances, cases, dials, caps, and all other parts that have now to be made and fitted specially to each movement. It need scarcely be asked whether the general adoption by the trade of such a system would not at one and the same time make the trade less fluctuating, promote a more complete division of the labour, cheapen the cost of production, yet enable the workman to increase his earnings, produce greater uniformity in the style and finish of the work, and expedite the manufacturing process very considerably.

Having now at some length set forth what consider should be done, it may be required that we should indicate the means whereby the general adop tion of such a system might be brought about, and the details fully considered and determined upon.

The first step to be taken would be to fix upon the measure which shall determine the scale of sizes. the choice of which lies between-firstly, the French metre, or milimetre, two of which are equivalent to 078 of an inch, nearly; secondly, the French line, equivalent to 089 of an inch, nearly; and thirdly, the 10th of an inch, to which latter measurement we have given the preference because it is English, and therefore a proper standard for the measurement of English watchwork. This gives a dial 15 or 14in. in diameter. being proportionate for a full 8-size movement; the next size with dial 1-6in. in diameter, the movement proportionate to which would be equivalent to an 11-size movement; next size with dial 1-7in. in diameter, proportionate to 14-size movement; next size with dial 1-8in. in diameter, proportionate to 17-size movement; next size, with dial 1-9in. in diameter, proportionate to 20-size movement; which, within the range from eight to twenty, gives five sizes of movement, in place of the seven sizes usually made and expressed as 8, 10, 12, 14, 16, 18, and 20 sizes respectively, but 8, 10, 12, &c., what, no one can tell. For larger or smaller sizes the same scale would be maintained; and that the difference in size that would be established by the universal adoption of this scale of measurement would suffice for all requirements of the trade, may be adduced from the fact that Messrs. John Ryley & Co., of Coventry, have for the last three years successfully put the system in practice, having had all their movements made to plates giving the calliper exactly proportioned throughout to the sizes proved it of immense advantage in reducing the of dials indicated above, and their experience has inanufacturing process to an easy working system, and ensuring uniformity not attainable by any other means, the system being adopted not only for the improved full-plate movements, but also for all the inade and finished by them. patent-plate centre-seconds and -plate movements

effected in the manufacture.
movement maker uses a different gauge (which he THE MICROSCOPE.*-CHOICE OF A MICRO-
does not understand), and adopts a different calliper,
based on his individual experience, the result of
which is that there will be nearly as much difference

TELESCOPIC WORK FOR MOONLIGHT in the same nominal sizes of two different makers as

EVENINGS.*

SCOPE.

of the year purchasing a microscope w which to begin the investigation of animal si vegetable structures. Others who would wish to on the one hand and by the fear of obtaining a invest in an instrument are deterred by the expense worthless thing on the other. Too strong a protes cannot be made against the notions prevalent with regard to microscopes, and encouraged by most of the makers in this country. The handsome-looking instrument of great size, with its long tube and innumerable wheels, is not to be recommended to

EDICAL and other students are at this time

there is supposed to be difference between two consecutive sizes of watch movements. We say adAN, interesting lunar region, that has been very difference is not even established, and is as variable visedly "supposed" difference, because the actual inadequately described, is found on the northern hemisphere of the Moon, between the as the gauges generally made use of, which have an well-known spot Plato and the lowest edge or limb unmarked and undefined space of varied length, and of the Moon as seen in an inverting telescope. give a result which cannot be definitely expressed This region, which is situated between the craters by any known scale of measurement. The approxiFontenelle, Timæus, and Epigenes, of Beer and mate difference, however, between the diameter of Mädler, comes into sunlight about and just after consecutive sizes of watch frames of the same make the would-be observer, even should he feel justified the first quarter. Beer and Madler speak of it as will be found to be 07, or about the fourteenth part calculated to "throw the observer into the highest of an inch, which difference is so small that the in the expenditure. The microscopes which are various sizes of movements in finished watches are used in most of the Germau laboratories, where so astonishment," and certainly as the Sun rises upon it and illuminates one after another the ridges of not readily determinable, and a greater multiplicity much thorough work is done (to the writer's knowmountains which compose it, it is a magnificent of sizes is created than there is any necessity for. ledge in Prof. Stricker's and Prof. Rokitansky's spectacle. The three leading objects, the craters within the same range six sizes to their five. at Leipzig, and in Prof. Claude Bernard's at Parasi, In comparison with the Swiss system we have laboratories at Vienna, in Prof. Schweigger Sadd's their sizes being regulated by the diameter of are the little instruments of Hartnack, which do Celestial Objects for the dials in French lines, but even this division we not stand above 10in. high, with a simple but large hold to be somewhat smaller than it might be. It stage without any movement, no rackwork to the would quite suffice if the difference were established tube, but a sliding motion and a fine adjustment. as the tenth of an inch in the diameter of the dials The instrument is used in the vertical position with between each size, the diameter of the top and complete comfort, and when liquid is on the stage. pillar plates, and all the other parts of the movement, this position being necessary, it is of considerable being proportioned thereto by a gauge divided to advantage to have a small microscope over which one can easily bend the head. Large microscopes. the tenth and hundredth part of an imperial inch. with their complicated machinery, are made to snit This division would give us five sizes of watch movement instead of seven, now cominonly made. the optician who sells them, and not for the conFixed diameters should also be determined for the Venience of the observer. Those who wish to get a microscope should insist either on having one of balances, wheels, barrel, &c., and every flat movement of the same size should have the same height these small and handy instruments made, or order of cost, a larger sum may be expended on the really a body having been purchased at a very minimum essential part of the apparatus-namely, the lenses. And here it will be found of great advantage to have the tube of the microscope not more than three and a half or four inches in length, for then the ob the greatest advantage, though, with proper care as

above-named, which may easily be found by means
of Webb's index map in his
Common Telescopes," are the three angular points
of the region. It is naturally divided into two
distinct areas, and is bounded on the south by the
Mare Fgoris. The western division consists of
very rugged land, the principal feature being a bold
promontory, more or less cleft, which stretches
into the Mare Frigoris towards Plato. Between
the rugged land on the west, and a very indivi-
dualized depressed surface on the east, a sinuous
mountain-chain extends from the promontory
above-named to the fine bold eastern portion of the
rim of Epigenes.
This crater is an interesting

instance of a feature by no means uncommon on the of pillar with its plates of the same thickness and one from M. Verick or M. Hartnack in Paris. Such Moon, viz., portions of wailed plains occuring in hollows sunk the same depth, which will enable the extensive lines of cliffs or mountains. In many instances the cliffs are interrupted or broken, so as manufacture to get the wheels, &c., pivoted to to form extensive bays on the surfaces of the plains tant division in the work the gauges, thereby creating another imporand bold promontories at the points of their inosThe calliper of culation. The west border of Epigenes forms a every movement of the same size should also be the same size throughout, and all sizes portion of another range, west of and nearly should be of a calliper similarly proportioned to jectives of the continental makers can be used with the fixed diameter of their dials. The exact radius

parallel with the before-mentioned chain of moun

By W. R. BIRT, F.R.A.S., in the Student.

* By BORTHWICK SMITH, in Horological Journal.

* From Nature.

to the ocular or eye-piece, they may be used on our ordinary long-tubed awkward English microscope. It is almost incredible that the English makers of object-glasses continue to demand three, or even four, times the price for their lenses which foreign makers do for lenses in every respect as good. For two pounds an object-glass may be obtained of M. Verick or M. Hartnack, of Paris, No. 8, which is quite as good a glass and in some respects more pleasant to use than the one-eighth, for which English opticians demand eight guineas. Many persons anxious to work with the microscope are deterred by the price of really first-rate instruments in this country. What we urge upon them most earnestly is to purchase such a body with eye-piece as that described above-simple but strong and steady for between two and three pounds, and to equip the instrument with the objectives of MM. Verick or Hartnack, say No. 2, No. 5, and No. 8, which can be obtained for another four pounds. We shall have occasion again to speak of the merits of English and foreign objectives, especially of the immersion object-glasses. At present we speak from personal experience, and desire to point out the convenience and cheapness of the small microscope-body, and the thorough excellence and iramensely diminished cost of the French makers object-glasses.

leading into a cylindrical chamber, at the bottom of

bluish

washing a thorough one, most cellular structures on the sun's disc one very large, round, and well-
are very beautifully and clearly brought out. Where defined spot; on one side, however, the penumbra was
rapidity is desired, and for the purpose of inspecting invaded by two tongues of facula for a short distance,
a specimen, it may be simply mounted in glycerine and in the centre of the umbra was a bright patch."
after the staining. The process above described is
that of Gerlach and Stieda, and is preferred to any
other by some observers of great experience. Thus
Dr. Meynert, of the lunatic asylum at Vienna, who
is throughout Germany regarded as the great
authority on the histology of the brain, uses this
method for mounting his sections of cerebrum,
cerebellum, &c. It is very convenient to have
little glass dishes with covers for each of the
above-mentioned re-agents, so that the sections may
be passed from one to the other and left covered up
if desired, for a day or two-the waste of re-agents
involved in filling watch-glasses each time they
are required being also avoided. If prepara-
tions have been preserved in chromic acid,
they must be very well washed before staining,
and very often cannot be made to stain well at all.
Various methods are useful in various cases, but, as
one of great general use, the carmine staining and
oil of cloves clearing may be strongly recommended.
Staining tissues with nitrate of silver, chloride of
gold, and with bile-pigment are most important aids
to the histologist, the merits of which have been
recently much discussed, and of which we shall have
a word to say from experience.

Glycerine Jelly.-This composition, which has been lately introduced, melts at a lower temperature than Deane's medium, and has a greater clearing action on the objects mounted in it. A small piece of the jelly put on a glass slip and warmed, soon liquefies, and is ready to receive any object, after which the cover is directly applied. For objects which do not require any great amount of "clear ing," it is a most useful medium. Insects, worms, small crustacea, &c., may be mounted in this way excellently.

E. RAY LANKESTER.

SCIENTIFIC SOCIETIES.

THE OBSERVING ASTRONOMICAL SOCIETY.
HoN. SEC-WILLIAM F. DENNING, Ashley-road, Bristol.
Report of observations made by the members during the
period from May 7 to July 6, 1870, inclusive.
PHENOMENA.-Mr. John Birmingham,

SOLAR R, Notes remarkable obscuration

of

Association; 80

Cutting Sections of Tissues.-The method of embedding," first practised by Stricker and Klebs, is now extensively used in Germany, and is of very great assistance to the practical histologist. It consists simply in surrounding the object from which sections are desired, with either paraffin, stearine, or a mixture of wax and oil. This latter is preferred at Vienna by Prof. Stricker and Dr. Klein, his assistant, and can be obtained of the exact consistency which may be desired; usually equal parts are to be used. A little tray of paper is made, and some of the wax composition in a melted state is poured in. The object to be cut is then placed in the tray, and more composition added, till the object is thoroughly enclosed. When hard, sections of the mass can be cut, the advantage being, in the case of thin laminæ or processes, that a complete support is offered by the surrounding compo sition, and a uniformly thin cutting may be obtained. For some purposes the microtome of Dr. Ranvier, of Paris, is very useful; it is similar to one recently brought out by Mr. Stirling, of the Anatomical Museum, Edinburgh. In this little instrument we have a flat piece of brass with a hole in the centre, which a screw works. A piece of elder-pith is ex- of the sun was observed here on May 22. It lasted cavated, so as to hold the tissue to be cut; and from sunrise to sunset, with a short interval in the when this has been well fixed in it, the pith is afternoon of returning brightness. The sun was of a squeezed into the cylindrical box through the hole beautiful pink colour, though there was no fog what in the brass plate. A razor drawn along the sur- ever, and its light was so reduced as to permit a long face of the brass plate cuts through the pith and observation of it through the telescope, without the the tissue it embraces, leaving a surface perfectly aid of a dark glass. I am informed that the same smooth and continuous with that of the plate. A phenomenon was noticed in the South of England on turn of the screw, which works into the cylindrical the next day (the 23rd), and on that day also, but late box, now causes a certain very small thickness of in the afternoon, it was observed at Rohrbach (Moselle), the pith and tissue to project above the plate, and and described by M. Hamat in a letter to the Scientific the razor again drawn across and pressed on to the that the cause of the obscuration, surface of the brass plate, cuts a fine section, the whatever it was, seems to have been moving eastward and southward." Mr. T. W. Backhouse, of Sunderland, exact thickness of which may be nicely regulated by the screw which pushes up the pith. This little in reports that in May "there was a remarkable case of strument may be obtained at a small cost from M. occurred with respect to the two largest spots of a a solar spot making a revolution round another. It Verick, 2, Rue de la Parcheminnerie, Rue St. Jac-group that was half away across the northern zone, on ques, Paris. It is not unlike an instrument de- May 9. The smaller spot was south of the larger, on scribed in English books on the microscope for the 7th, at 3h., but preceded it on the 12th, at 21h., cutting sections of wood, but its application with the line joining the two spots having rotated the use of pith, previously much in use for making through an angle of 80 or 90 in 5 days. This sandwiches with delicate tissues which had to be movement continued to the 15th, but this would cut, increases its value greatly. As to knives to be be partly apparent, owing to the group approaching used in making sections, though some large knives the limb. By that time the larger spot was reduced to are made on purpose, there is nothing better than a the size of the other. I cannot say whether the motion first-rate broad-bladed razor. Dr. Meynert has cut was a curved or a straight line, though it was probably his immense collection of brain preparations with a the former; nor can I say which of the spots moved, or whether both did. They were about 22,000 miles apart on the 9th, at 3h., but on the 13th, at 20h., they were 32,000 miles apart. One spot must therefore have moved, relatively to the other, about 34,000 miles, in 4 days, or at the rate of 300 miles per hour." "Mr. observed during June were, with the exception of one T. G. E. Elger, of Bedford, says: "The sun spots small and devoid of interest when compared with those seen in April and May. The largest spots were confined to the sun's northern hemisphere. Between the 8th and 15th the spots were all small; on the latter date there were only two groups on the dise, and these were insignificant. On the 19th a very remarkable spot was observed, it formed the preceding member of a large scattered group 2 52" in length; its penumbra measured about 1' 10" in greatest diameter. At 10 a.m., an isolated mass of light, intensely bright, was remarked on the nucleus; this at 2 p.m. formed a "bridge" connecting adjacent sides of the umbra. The nucleus of this spot was very uneven in colour. At 5h. 15m. p.m., on the 19th, the central portion was noted as brown and the border as black, and on subsequent dates the variety of tint was still more marked. At 7 a.m., on the 21st., when the penumbra showed evident signs of cyclonic action, not more than half the area of the nucleus was black, the remainder was made up of patches of various shades of brown. The group disappeared at the limb on the 27th." The Rev. S. J. Johnson, of Crediton, observed numerous spots on the sun on May 13th. There were then four groups with penumbra close together. W. H. Michel Whitley, of Penarth, says: June 21, I noted

common razor.

Staining and Mounting Tissues.-The method which is now very extensively used in German histological laboratories for the study and preservation of all kinds of delicate tissues, such as sections of the developing hen's egg morbid growths, fine injections, nerve tissues, &c., is as follows:-The section, either from a fresh specimen or from one preserved in alcohol, is placed in a solution of carmine in ammonia, from which all excess of ammonia has been allowed to evaporate, as tested by the smell. The solution is also carefully filtered before use, and diluted to a small extent. After from three to ten minutes or more in the carmine solution, the section is placed in distilled water and thoroughly washed for some time by blowing into the water with a small pipette. From this the section is removed momentarily to a watchglass containing distilled water and two drops of acetic acid, and then is placed in absolute alcohol.

The water is thus removed, and in five or ten minutes the section may be placed in oil of cloves, which renders it very transparent. From this it is removed to the glass slip, and is mounted in a solution of gum damara in turpentine, such as is sold by artists' colourmen. At any stage in this process we can proceed back again by the same steps, ammonia being used in place of acetic acid, and re-stain, rewash, or re-acidify as the case may be. If the staining is carefully managed and the subsequent

group,

THE PLANET SATURN.-Mr. H. Michell Whitley repeatedly observed this object with his 6in. reflector. He says:- June 21.-Air very unsteady, but after midnight better.-The Ball: Duller yellow than rings; equatorial zone yellow; north of this a pale red belt, and another further north again towards pole, much fainter, and about midway. Pole of planet grey, edges of ball slightly shaded; no other spots or markings.-Ring 4: Inferior in brightness to B; colour pale division: Traced all round; widest and darkest, if at yellow; no subdivisions or markings on it.-Ball's all, in W. Ansa; sharply defined in colour, it was not so black as the sky, but deeper than the crape ring across the ball; colour dusky.-Ring B: This ring was very bright for a short distance from its outer edge, which was very sharply defined; colour gradually deepens and light fades towards inner edge; outer edge lemon yellow; duller and deeper inwards; strongly suspected to be shaded, but no actual subdivision seen. of light on inner edge of ring which was not sharply defined.-Ring C or crape ring: Very delicate colour, dusky purple; I could with care, as a very fine object, trace the edge of the globe through it up to ring B., equally distinct in E. and W. Ansa. No markings of any kind upon it. June 28.-10h. to 11h. 15m., power 250, definition very flattering. North equatorial ruddy belt very distinct. Equatorial yellow band the brightest part of the planet. Between the north equatorial ruddy belt and north pole, lay one or Pole pale bluish grey. very faint ruddy bands. distinctjacross the ball. July 2.-10h., definition very No other markings. The crape ring very dark and sharp, power 250, a glimpse observation. The two belts before mentioned very much plainer and darker than on June 21, 28, and not of such a ruddy hue."

No line

more

LUNAR OBSERVATIONS.-Mr. John Birmingham, of Tuam, Ireland, reports that on June 6th he saw "a very marked central depression in the white spot of Linné, though the Terminator was so far away as the boundary between the Mare and the Palus Putridinus. The depression was rather east of the exact centre of the white spot, so that the western exterior slope was longer than the eastern." Mr. H. Michell Whitley has observed, with great care, many interesting and difficult lunar objects, and the results of his observations have been sent to Mr. W. R. Birt, F.R.A.S.

WINNECKE'S COMET.-Mr. George J. Walker, of Teignmouth, observed this body on June 5th, 6th, and 7th, and he says that it looked like a tolerably bright nebula." On the 6th, at 14h. 13m., the comet looked

faint, owing to the strong twilight.

METEORS.-Mr. G. J. Walker saw a splendid meteor on June 24th. It traversed the greater part of the sky, and was much larger and brighter than Venus. It was of a blue colour. Mr. Walker adds, "I think it appeared a little to the right of Altair, and passed near Vega, and on to the Pointers in Ursa Major; it had a magnificent train, and, I think, must have traversed an are of about 120°. The time of its appearance, as well as I could make out from my watch, was 11h. 18m. Greenwich mean time, and it may have been 7 or 8 seconds making its sweep over the heavens. I did not hear any sound with it." Mr. H. M. Whitley observed a brilliant meteor on June 29th, at 11h. 30m. It was of the second magnitude-"pale yellow, velocity very great."

66

A NEW RED STAR.- Mr. John Birmingham haz believe, previously noticed; at least it is not in frequently observed a red star in Cygnus, not, I which gives a list of all the red stars known up to 1866. Schjellerup's Catalogue " (Ast. Nach., No. 1591), It is of a deep red, of about the eighth magnitude, and position, compared with 32 Cyani, is about R. A. 20h. is near a blue star of the same size. Its approximate 15m. 37s. Declin. + 47° 27′ 28"."

OCCULTATION.-Mr. Walker witnessed the occultation

of e Libræ on June 11th, and found that the exact time of disappearance was 9h. 27m. 55-6s. Greenwich mean time.

EXPORTS OF MACHINERY.-During the first four months of the present year the value of the steamengines and machinery exported from the United Kingdom showed a sensible improvement as compared with the corresponding period of 1839. Steam-engines £575,041, as compared with £409,492 in the first four were exported, to April 30th this year, to the value of months of 1869, and £431,472 to the corresponding date of 1868. The increase observable this year was chiefly attributable to the greater demand for steam-engines from Egypt, which took them to the value of £105,424 in the first four months of this year, against £29,054 in 1869, and £18,259 in 1868. General machinery was exported to April 30th this year to the value of £957,670, as compared with £848,934 in the corresponding period of

1869, and £725,960 in 1868. There was an increase this year in the exports to France, Spain, Egypt, and Australia; and a decrease to Russia, the Hanse Towns, Holland, Belgium, and British India.

AN ATMOSPHERIC TELEGRAPH.-A novel kind of telegraph, the invention of Signor Guattari, an Italian, was submitted to the inspection of a party of scientific gentlemen on Monday week, at a private house in Gloucester-st., Warwick-sq. The inventor aims at obtaining by the use of atmospheric power the same or better results than those attained by electric and magnetic forces To this end he charges a reservoir with compressed air and, by the operation of valves worked in the same sends pulsations through a tube, which pulsations are manner as those in use in the ordinary telegraph system, made to work upon the receiving instrument with an effect corresponding with that of the electric current passed along insulated wires.