a disruptive discharge. By the means above described a current of enormous frequency is produced. To convert this into a working current of very high potential, in the circuit A is connected the primary P of an induction coil having a long fine wire secondary S. The current in the primary P' develops in the secondary S' a current or electrical effect of corresponding frequency, but of enormous difference of potential, and the secondary S' thus becomes the source of the energy to be applied to the purpose of producing light. The light-giving devices may be connected to either terminal of the secondary S'. If desired, one terminal may be connected to a conducting wall of a room or space to be lighted, and the other arranged for connection of the lamps therewith. In such case the walls should be coated with some metallic or conducting substance in order that they may have sufficient conductivity. The lamps or light-giving devices may be an ordinary incandescent lamp; specially designed lamps are now preferred, how ever. This lamp consists of a rarefied or exhausted bulb or globe which incloses a refractory conducting body, as carbon, of comparatively small bulk and any desired shape. This body is to be connected to the secondary by one or more conductors sealed in the glass, as in ordinary lamps, or is arranged to be inductively connected thereto. For this last named purpose the body is in electrical contact with a metallic sheet in the interior of the neck of the globe, and on the outside of said neck is a second sheet which is to be connected with the source of current. These two sheets form the armatures of a condenser, and by them the currents or potentials are developed in the light-giving body. As many lamps of this or other kinds may be connected to the terminal of S', as the energy supplied is capable of maintaining at incandescence. In Fig. 3, is a rarefied or exhausted glass globe in which is a body of carbon e. To this is connected a metallic conductor, f, which passes through and is sealed in the glass wall of the globe, outside of which it is united to a copper or other wire, g, by means of which it is to be electrically connected to one pole or terminal of the source of current. Outside of the globe the conducting wires are protected by a coating of insulation,, of any suitable kind, and inside the globe the supporting wire is inclosed in and insulated by a tube or coating, k, of a refractory insulating substance, such as pipeclay or the like. A reflecting plate, 1, is shown applied to the outside of the globe b. This form of lamp is a type of those designed for direct electrical connection with one terminal of the source of current; but there need not be a direct connection, for the carbon or other illuminating body may be rendered luminous by inductive action of the current thereon, and this may be brought about in several ways. The preferred form of lamp for this purpose is shown in Fig. 2. In this figure the globe b is formed with a cylindrical neck, within which is a tube or sheet, m, of conducting material on the side and over the end of a cylinder or plug, n, of any suitable insulating material. The lower edges of this tube are in electrical contact with a metallic plate, o, secured to the cylinder n, all the exposed surfaces of such plate and of the other conductors being carefully coated and protected by insulation. The light-giving body e, in this case a straight stem of carbon, is electrically connected with the said plate by a wire or conductor similar to the wire f, Fig. 3, which is coated in like manner with a refractory insulating material, k. The neck of the globe fits into a socket composed of an insulating tube or cylinder, p, with a more or less complete metallic lining, s, electrically connected by a metallic head or plate, r, with a conductor, g, that is to be attached to one pole of the source of current. The metallic linings and the sheet m thus compose the plates or armatures of a condenser.-Electrical Review (N.Y.) THE ELECTRIC TRANSMISSION OF POWER.*-II. power actually delivered to the motor, and that which might be so delivered if the battery were used for working a motor at the charging station itself; in other words, if the distance of transmission were nought. Say, for instance, that a total of 1,000H.P. hours could be obtained from the battery, if it were discharged immediately, and that the power spent in the outward journey amounts to 50H.P. hours, then a further 50H.P. hours will have to be spent in the return journey, and the power obtainable at the mill will only amount to 900H.P. hours. The efficiency of transmission will, in this case, be 90 per cent. If we double the distance between the waterfall and the mill, the efficiency of transmission would be reduced to 80 per cent.; if we treble the distance, the efficiency would only be 70 per cent., and so on. efficiency must depend on the road over which the transmission takes place; it will be smaller on a common road, larger on a tramway, larger still on a railway, and largest on a canal. We can, for every arrangement, express the value of the system, as far as economy of power is concerned, in one of two ways. We can, if the distance is fixed, give the efficiency in the usual way as a percentage, or we can fix a standard percentage of efficiency, and ascertain the distance over which this standard is attainable in any particular case. I shall adopt the latter way of reckoning as the more convenient for comparison with other methods for transmitting power, whether in stored or live form. The First, as to transmission of stored power otherwise than by batteries. The only two methods we need consider are the carriage of corn and the carriage of coal, each combined with the use of a proper engine for converting the stored into live power at the other terminus of the line of transmission. In the case of corn, the starting point of this line is the field where the corn is grown. We there load it into suitable vehicles, and send it to the mill where the power is wanted. Since we are dealing now entirely with animal power, we must suppose the cartage to be effected by draft animals say horses-and the conversion of corn into live power at the mill also by such animals. I need hardly say that, at the present time, no English mill-owner would dream of working his mill in this fashion by animal power, since coal is yet abundant, and a single steam-engine is a far cheaper and handier instrument for producing and controlling a larger amount of power than an equivalent number of horses. On the other hand, if power is required in small quantities, and in particular ways, then the horse will produce this power better, more cheaply, and more conveniently than the steam-engine. It may seem absurd to work a large cotton-mill byhorse-gear; but substitute for the mill a farm, and you see at once that the transmission of stored power to it, in the shape of corn, is a necessary part of the agricultural operations. Now, the horses, in bringing the corn to the place where the power is required, perform work, and must consume an equivalent amount of food. They also perform work in bringing the empty carts back again to the field to re-charged. The ratio between the amount be of corn delivered at the mill and the amount taken out of the field would therefore represent the efficiency of transmission. If this is to be 90 per cent., as in the case of electric transmission, we may take it that, for every 100 sacks of corn taken away from the field, the horses would eat on the outward journey (when the carts are heavily laden) 6 sacks, and on the homeward journey (when they are empty) 3 sacks, leaving 90 sacks of corn to be converted into live power at the mill. The distance to which we can thus carry stored power with a standard efficiency of transmission is a measure of the merit of the system, as far as economy of power is concerned. The transmission of stored power in the shape of fuel is a parallel case. We load the coal at the pit's mouth into waggons, and haul them by means of locomotive engines to the places where the power is wanted. Part of the coal is consumed on the outward and homeward journey of the train, 100 tons put on the train at the pit's mouth, we leaving the rest for the production of live power at the mill. If this amounts to 90 tons out of every have again an efficiency of transmission of Alic works, and an electric station where the four miles on all kinds of road where corn is the transmitting agent. In all cases I have assumed that the road is the best of its kind, perfectly free from gradients or curves, and that the traffic can be worked at the speeds mentioned without interruption. In reality, these conditions will, of course, not all be fulfilled; we have to make allowances for waste of power on gradients, curves, bad places in the road, for running at variable speed, and for stopping and starting. The distances given in the table are, therefore, throughout too large; but, as our purpose is merely the comparison of the different systems, we may take the figures in the table as a rough indication of the merits of each. TRAMSMISSION OF STORED POWER. efficiency, the electric transmission of stored power You will see, from this table, that as regards cannot compete with the other two methods. horse and cart carrying corn over an ordinary electric locomotive taking batteries over a railway. carriage road works with twice the efficiency of the The discrepancy is still greater if we compare the electric locomotive hauling batteries with the steam locomotive hauling coal. The latter can transmit power over a distance fifty times that over which the former can transmit power with an equal efficiency. On a tram line the distance over which cent. is, according to the table, 10 miles; that is to we can transmit power with an efficiency of 90 per say, if the whole load of the car is composed of batteries, we can run it 10 miles out and 10 miles home at an expenditure of 10 per cent. of the total this compares with the storage cars in use on charge of the batteries. Now let us see how passenger tram lines. The total weight of a full-sized car is about 10 tons, made up somewhat as follows:-Car and propelling gear, tons; batteries, 2 tons; passengers, 3 tons. If the 3 tons represented by the passengers were utilised for additional storage cells, the car could run 20 miles with the loss of 10 per cent. of its charge; or it could run 200 miles if losing the 24 tons of batteries instead of 6 tons, it can only whole of its charge. As there are, however, only run 86 miles. This is according to the table, and more than attainable in practice, for the reasons already stated. Experience has shown that storage cars can only run from 30 to 60 miles with one set of batteries, or half the distance stated in the table. If we apply the same reduction to all the methods of transmission, we find that the distances to stored form, with an efficiency of 90 per cent., are which power can be carried electrically in the two, five, and eighteen miles over a carriage road, tramway, and railway respectively. The efficiency of transmission is, however, not the only or even the most important consideration in the problem of transmitting power to a dist ance. The owner of a transmission plant cares nothing for any theoretical perfection in the way of high efficiency. All he cares for is the cost at which the power is delivered to him. All other things being equal, high efficiency will naturally reduce this cost, and, in so far, is an advantage; but in practice all other things are not equal, and to aim at high efficiency regardless of other con siderations is the reverse of good engineering. It is no doubt gratifying to the engineer if he can point to a transmission plant designed by him to give some extraordinarily high efficiency; but if this result has been obtained by means of an exorbitant capital outlay and excessive working expenses, it will not be equally gratifying to his employer, the owner of the installation, who has to pay for its erection and working. It therefore becomes the duty of the engineer so to plan the installalation that the cost of the power delivered shall be a minimum under any given circumstances. to which we can carry power by either of the three agents here mentioned (namely, batteries, corn, and We have seen that, judged by the efficiency coal) depends very much on the kind of road over standard alone, electric transmission of power in which the transmission takes place. We might the stored form is hopelessly behind the other two our object is to obtain a rough general comparison see whether this is or is not the case, if we assume an almost infinite variety of cases, but, as methods which we compared with it. Let us now of the different systems rather figures for any one of them, I have assumed the only reliable test of cost. It is, of course, than exact judge the system by the more practical, and, indeed, merely three kinds of roads-namely, a com- understood that, in estimating the annual cost at so margin of power for taking the train back to the and have calculated the distance to which power into account not only the cost of coal burnt mon carriage road, a tramway, and railway, many pounds per horse-power delivered, we take charging station. The economy of the whole system can be transmitted in each case with a loss of throughout the year, if we obtain the power by will evidently be the greater the less power is spent 10 per cent. The results of these calculations are steam, or the rent for water if we use a turbine, but in the outward and home journey; and we might also all other expenses which may properly be call "efficiency of transmission" the ratio of the charged to the power account, such as wages for By GISBERT KAPP. Extracted from the Cantor the attendants, petty stores, interest, repairs, and Lectures delivered before the Society of Arts. depreciation of plant. Estimated in this way, exhausted, because we must allow a sufficient given in the following table. The speed of transmission has been assumed at four, six, and twenty miles for road, tram, and rail respectively, when coal or batteries are the transmitting agents; and at the cost of water power will be found to vary between £2 and £8 per annum, the exact figure depending, of course, on the total amount of power available, the quantity of water, its fall and local conditions, which must largely influence the cost of the hydraulic works. The cases where waterpower can be had at so low a price as £2 a year are exceptional; on the other hand, if we have to pay as much as £8 a year for water-power, it will seldom be worth while to transmit it electrically, or in any other way; and I shall, therefore, assume £3 or £6 as the limits of cost for water-power intended for electric transmission. The cost of steam power, if produced by large economical engines, is generally taken at £10 per year; if produced by small, and therefore less economical engines, it may rise to £20, and even £40 per year. I shall further assume that in all cases the power is required for 3,000 hours during the year, that is, 300 working days of 10 hours. At the outset, it is clear that if we wish to transmit large parcels of power-say 100H.P. and upwards-by storage batteries, we must be able to deliver the power at a cost higher; it would obviously pay better to establish a local steam-engine. I have already mentioned that a system of battery transmission can be made to yield 56 per cent efficiency, if we allow 10 per cent. for the transmission itself. To deliver 100H.P. we must, therefore, charge with 178H.P. during a time equal to that during which the power is required. If, therefore, at the generating station the annual horse-power costs £3, the charge for power alone will be £5 6s. at the receiving station. To this must be added the cost of labour and the interest and depreciation of plant, which, in this case, consists of the generating dynamo, motor batteries, and line of transmission, with its equipment of locomotives and waggons. The small storage cells, as now made, for lighting and power purposes, cost about £40 per horse-power; but let us assume that the larger cells, such as we would require, could be had for £30 per horse-power, then a battery to work a 100H.P. motor would cost £3,300. In order to economise carriage, and to reduce the wear and tear of cells, it would be advantageous to have two batteries, one being charged while the other is at work. We have thus an initial outlay of £6,660 for batteries alone. The interest and depreciation on these will certainly not be less than 15 per cent., or £10 per horsepower. Add to this, the cost of power at the generating station, that of labour and interest and depreciation on the electric machinery and the line, and you will see that it is quite impossible to compete with battery transmission against a local steam-engine, if the power produced by the latter costs £10 per annum. But how does the case stand, if the amount of power required is so small that it cannot be produced at this low figure? If we want only 5H.P., and if we produce it by a local steam or gas-engine, we shall have to pay for each horse-power £20 to £40 per annum. Will it, in this case, pay to transmit, by means of batteries, the power produced by a large and economical steam engine at some central station? If we have to build a tramway or railway for this purpose specially, it will certainly not pay; but let us assume that a tramway already exists, and let us investigate whether the company-which, we suppose, is working the line by storage cars-could afford to sell to a customer on the line power at a cheaper rate than he could produce by a local engine. Let us assume, by way of example, that the customer requires 5H.P. for 10 hours daily. The battery to work a 5H.P. motor will weigh about 2 tons, and cost £170. The charging dynamo, motor, and regulating gear will cost about £150, so that the whole capital outlay, if we provide two batteries, will amount to £490. (To be continued.) THE MAXIM AEROPLANE. THE following account of the Maxim aeroplane given by the inventor:-My experiments have not been in the realm of ballooning, but on the aeroplane system-to propel a plane set at an angle so as to ride on the air as fast as the air yields, and so to keep up an approximately straight course. I put up a steel column, with a long wooden arm arranged to rotate on the top of the column; an arm pivoted to the column, simply to swing around, and long enough to describe a circle exactly 200ft. in circumference. This arm was stayed in every direction so as to be perfectly stiff, and it was as sharp as a knife, so as to offer very little resistance to the air. To the end of this arm I attached what might be called a small flying machine, arranged in such a manner that power could be transmitted to the machine through the post and arm. The machine had a steel shaft that could be rotated at any speed, and was also provided with a dynamometer, an instrument for measuring force. To this shaft of the flying-machine were attached various kinds of propeller screws-one at a time, which I caused to be rotated at various speeds. The apparatus when complete was arranged to correctly indicate the number of turns per minute, the actual push or propelling force of the screw, and the slip of the screw. When the arm was allowed to go free, and the screw was rotated at a high speed, the flying-machine would travel around the circle at from thirty to ninety miles an hour. The machine was also provided with a system of levers similar to those used in ordinary druggists' scales, and to this were attached planes, generally made of wood, and arranged in such a manner that they could be placed at any angle above the horizontal. By carefully measuring the power required for a certain speed without any plane attached, and then attaching the plane, and running the machine at exactly the same speed, the difference in the force required for both operations indicated the actual force required to propel the plane. that about 40H.P. will suffice after the machine has once been started, and that the consumption of fuel will be from 40lb. to 50lb. per hour. The machine is made with its present great length so as to give a man time to think; its length makes it easier to steer, and to change its angle in the air. Its quantity of power is so enormously great in proportion to its weight that it will quickly get its speed. It will rise in the air like a seagull if the engine be run at full speed while the machine is held fast to the track and if it is then suddenly loosened and let go. If it were necessary it could mount right up, spirally, around and around in a circle of a mile in circumference in its own country. It If it proves as I have figured it, there should be room for fuel to carry it 1,000 miles; indeed, it looks as if it might carry two tons of fuel, or sufficient to propel it across the ocean. But I cannot tell about that; a trial alone will determine what unforeseen things, not calculated, will arise. will be possible to burn 2001b. of fuel an hour; but I figure that 40lb. or 50lb. will produce a moderate speed, or for high speed, 1001b. The highest speed I got the small machine was 90 miles an hours; but I believe this big one will go 100 miles an hour. If it goes at all, I shall be very happy; but on the basis of my figuring it ought to be able to develop between 250H.P. and 300H.P., and it ought to carry 9,000lb., or 1,400lb. with its own weight included. In warfare it would not need to carry so very much. Two men will be enoughtwo men and a little dynamite-a ton, or a couple of tons. As to the wind, the winds are as apt to be favourable as unfavourable; but at a certain distance from the earth they cease to be formidable. You are always in a dead calm at a certain distance on high. Gales are narrow things; they don't disturb much space. Moreover, their strength and speed have been very much exaggerated in the popular mind. Let us suppose we are encountering a wind at 40 miles an hour-a very unusual speed-then, if the machine is regulated to go 60 miles an hour, it will travel 20 miles against the wind, or 100 miles with it. The apparatus for holding the plane was provided with a carefully-made dynamometer, which measured and registered the lift of the plane-the amount it would lift when being driven through the air. When these planes were perfectly horizontal, and the machine was allowed to travel at a high velocity nothing was registered; but if the front or advancing edge of the plane was raised slightly above the horizontal-say 1 in 30-then it was found to have a tendency to rise. On one occasion, when a plane was placed at an angle of 1 in 25, it was found that it would carry 250lb. to the horsepower; but this result was only obtained on one occasion. The angle was so slight, and the speed was so high, that it was difficult to arrive at the same result the second time on account of the trembling of the plane in the air. The angle was accordingly changed, and nearly all subsequent experiments were tried with the plane placed at an angle of 1 in 14-that is, that when the plane advanced 14ft. it pressed the air down lft. In these experiments it was found that, with every pound of push given by the screw, 141b. could be carried by the plane. The skin friction on the screw and on the plane was so small as to be unappreciable; it was nothing like the friction of a screw in the water. With the angle of 1 in 14 everything ran smoothly, and experiments were tried with all speeds between 20 miles aud 90 miles an hour. These experiments proved that certainly as much as 133lb. could be carried with the expense of 1H.P. These are the data I personally obtained, and which I know to be true. They do not depend on theory at all. The small planes experimented with were from 2ft. to 13ft. long and from 6in. to 4ft. wide. Fifty different forms of screws or screw-propellers were used in conducting A these experiments. My large apparatus is provided with a plane 110ft. long and 40ft. wide, made of a frame of steel tubes covered with silk. Other smaller planes attached to this make up a plane, and to this are hinged various other planes, very much smaller, which are used for keeping the equilibrium correct and for keeping the flying machine at a fixed angle in the air. The whole apparatus, including the steering gear, is 145ft. long. The machine is provided with two compound engines, each weighing 3001b. The steam generator weighs 350lb. The other things-the casing about the generator, the pump, the steam-pipes, the burner, the propellers, and the shafting-all weigh 1,800lb. Everything is remarkably light, so remarkably light that one grate-bar in a boiler that generates as much steam as mine would weigh more than my whole boiler. It is made of copper and steel, brazed with silver solder. There are 48,000 brazed joints in the generator, and it is heated by 45,000 gas-jets, there being 40ft. of grate surface. The heat thus produced is perfectly terrific. The boiler was tested up to 9001b. pressure, and it didn't leak a drop. surface of 5,500sq.ft. There is one great central The most novel feature about the engine is the system by which I burn petroleum and generate steam. Petroleum is turned into gas, and then that is burned for generating steam. The engines have lately been tried, and it was found that they gave a push of 1,000lb. on the machine, which 14,000lb. The actual amount of power shown in useful effect upon the machine itself was 120H.P. A part of the aeroplane, or actual kite, is made of very thin metal, and serves as a very efficient condenser for the steam. It looks much like a kite indeed, that is what it is-a huge kite, with the machinery hanging beneath it from its under side. If it were in the air, in flight, you would see a great sheet of silk and a little platform under it, between it and the earth. The machine has not been tried, owing to my absence from England. It is ready and awaiting my return. It is now resting on a track 12ft. wide and half a mile long, in my park. The first quarter of a mile of the track is double-that is to say, the upper track is 3in. above the lower. By that means I am able to observe and measure the lift of the machine when it starts, because the upper track will hold it down when it lifts off the lower one. When completed, the machine will weigh, with water-tanks and fuel, somewhere between 5,000lb. and 6,000lb., and the power at my disposal will be 300H.P. in case I wish to use it; but it is expected As to what it will do, the whole world becomes changed if it works-the whole world will be revolutionised in a year. There will be no more ironclads, no more armour plates, no more big guns, no more fortifications, no more armies. There will be no way of guarding against what this machine will do. METHOD OF DRAWING MICROSCOPIC OBJECTS BY THE USE OF CO-ORDINATES. HE method which I am to detail is one that I It is a Tomt in use by Dr. George Marx, of the Division of Illustrations, in the U.S. Agricultural Department, when I first engaged in studying animal parasites in 1886, but it was originated some eight years earlier, as he informs me. method that has such obvious merits that I take pleasure in placing it before students of the microscope; but I present it as a relator of a valuable method rather than of original work. Its simplicity, its cheapness, its accuracy, the ease with which a figure of any magnification or reduction may be made, and the rapidity with which a beginner adapts himself to its use, all serve to recommend it. A small glass slide, of the size of any eye-piece micrometer, or a disc, ruled into squares, is inserted into the eye-piece, so that the lines seem to rest upon the object. Tracing paper is placed over cardboard ruled into squares. The drawing is then made free-hand, the various points being located in a symmetrical position with respect to the lines underlying the paper that they occupy in the apparently ruled image. The drawing made on the tracing-paper may then be either transferred to drawing-paper without reduction, or be reduced by applying the same methods that produced the picture, and then be worked up. Dr. Marx prefers is squares one mètre on each side, every third line being slightly deeper to make it more prominent. I prefer for most uses the finder made by Zeiss. It is a circular disc, upon the centre of which are ruled two sets of ten lines, at right angles to each other, the lines being five-tenths millimètre apart. The lines very neatly ruled, and covered by a thin cover-gla cemented to it with balsam. It is apparent that the system has a wider application so far as the magnifications to be attained are concerned. The equation giving the magnification is x= b x c. a a being the length of object, b the length of image, the ratio of the image to the drawn figure. Suppose that the amplification of objective is 5 x; that the lines on the eyepiece slide be one-half millimètre apart, and those on the cardboard be 6 millimètres, then x = 5 × 6 × 2, or 60, for the unit of By COOPER CURTICE, D.V.S., Moravia, N.Y., a paper read before the Washington Microscopical Society, 1891. squares. To use a series of objectives, or of squares for the eyepiece and for the cardboard are easy matters. A single glass ruled to half-millimètres made to fit a low-power eyepiece is sufficient to try the plan. Cardboards, either of Bristol board or heavycalendered manilla paper, may be ruled into squares 3, 5, or 7 millimètres, &c., until the student has all the combinations desirable. By adopting this plan of drawing figures, I have found that objections which I find to using the camera are avoided. The lighting is not interfered with, the image moves but little, if any, with the movement of the head, and the image can not be distorted. It is true that the accuracy of the figure depends on the skill of the artist, but a short trial of the method will satisfy most students that the actual variation of the drawing in symmetry from the image is less than that in figures made by the camera. The objection now existing that American makers have not on hand necessary slides will be gladly removed by them as soon as they see a demand. NECK.* spaced; and the accompanying diagram exhibits a It is to be understood that when the distance from order to avoid this, the spacing of the outer arc may be stopped at any convenient division, as L. The vertical by which that point is determined cuts BC at B', and through B' a new arc, B'L', is described. Through the points in which this arc cuts the radial passed, which will divide another portion of A Cas required, and by repeating this process the spacing of the whole neck may be effected by a diagram of reasonable size. the first fret is to be placed at th of that distance | lines already drawn, a new series of verticals is SPACING THE FRETS ON A BANJO from the nut, the distance from the first to the second is to beth of the remainder, and so on. To determine these distances by computation, then, is a simple enough, arithmetical exercise, but it is exceedingly tedious, since the denominators of the fractions involved increase with great rapidity; being successive powers of the comparatively large number 18, they soon become enormous. THE amateur performer on the banjo, if he be of a mechanical turn, is often tempted to exercise his skill by making an instrument for himself; and the temptation is the greater because he can confine himself to the essentials. The excellence of a banjo in respect to power and tone depends mainly upon the rim and the neck-that is, supposing the parchment head to be of proper quality; but then the preparation of the heads is a business of itself, and the amateur is no more expected to make the head than to make the strings. So, again, all the minor accessories, such as pegs and tail-pieces, brackets and bridges, are kept in stock for his benefit, and he may justly claim all the credit if his efforts in connection with the two principal parts first mentioned result in the production of a superior instrument. Among these ready-made items is a "fret wire" of peculiar section, furnished with a flange ready for insertion into fine saw-cuts across the neck, which much facilitates his work. Of course, the correctness of the notes depends entirely upon the accuracy with which the frets are By Prof. C. W. MACCORD. From the Scientific Ameri plement. In the large diagram, the distance AC on the horizontal line corresponds to the distance N B on the instrument. At A erect a vertical line, and mark upon it a point, B, such that BC shall be exactly eighteen times any convenient unit, BI. In the illustration B C is 26in., and BI is 1in., so that BC is 27in. in length. About C as a centre describe the arcs BL, IK, and through I draw a vertical line, cutting BL in D; draw the radius DC, cutting the inner arc IK in J, through J draw another vertical, cutting B L in E, and so on. = SHELL FLOWERS. Brittany, we had an opportunity of observing a recent excursion to the sea-coast of a very pretty method of utilising those thousands of brightly coloured shells that the sea shapes and polishes in its incessant working of the sand. It is both curious and interesting to see with what art, with what truthfulness, the majority of the flowers of our gardens are thus imitated. The reproduction, in Fig. 1, of one of these little masterpieces of patience and observation shows plainly with what perfection nature is represented. Practised in the first place in families, especially by little girls, this pleasing art, owing to the demands of bathers, has given rise to a sort of minor industry along our coasts. We have been pleased to study closely the manufacture of those flowerets, the brilliancy of which defies time, and it is the result of these observations of ours that we here record, happy if these few notes should prove of utility to our lady In the triangles ABC, 1 DC, 2 EC, we have BI 1. Cutting nippers. 2 and 3. Files. 4. Pincers. 5. Prepared semoule. 6. Starch paste.-Shells: a, carapace of They consist of a cutting nippers, 1, for cutting the wires of the stems, flat and half-round smooth files, 2 and 3, for trimming and shaping the edge of the shells, a fine pincers, 4, for grasping the small shells, a cup of mucilage of gum arabic, to which is added enough powdered starch to give it the consistency of honey, a few boxes of prepared semoule, 5, that is to say, coloured yellow or red for forming anthers; and, finally, an assortment of embossed leaves, tissue paper, iron wire, &c. readily found at the stores of all the shell dealers of The varieties employed are relatively few in One of the beings of the sea that furnishes the principal material of the floral industry is the barnacle (Anativa lævis, Lam.). This singular host of the ocean, which has the false aspect of a plant, has already been thoroughly described in this journal. The carapace comprises five pieces, of a beautiful milky white, two triangular shells which embrace the foot and protect the greater part of animal, and two other and smaller shells hinged to the preceding, and having a very elongated tri angular form. The double valves are united along one of the sides by a long narrow curved piece, the general form of which is that of a sickle. The shells are very light, and in order to separate them without injury to their inhabitants, they must be placed in an earthen pan and allowed to enter into decomposition. In a few days, the operation having terminated, they are washed with an abundance of water, and the valves, which easily separate, are collected by means of pincers. They are then immersed in a solution of hypochlorite of lime in order to free the edges of the last traces of hinges. The valves are now adapted for making numerous flowerets. It will be always well, however, to round off the base of these triangular plates by means of a file, and to perfect the edges and give to the whole the form of the petals of the flowers to be made. The hooks serve for making chrysanthemums or the barbules of the honeysuckle (Fig. 2, c). The large valves are employed for camellias, eglantines, white pinks, white roses, and periwinkles, and the small ones for verbenas, the jasmin, the clematis and double daisies. These being wound spirally upon a wire, at once Univalve shells, such as the limpets (Patella, Let us describe the manufacture of a camellia, which will serve as a type for the construction of all similar flowers, such as roses, &c. We take a wire of medium size and bend one extremity into the form of a loop, which, by means of gum, we fix to a cardboard disc of the size of a ten-cent piece, and which we cover with a hemispherical layer of white wax, previously softened by kneading it with the fingers. Alongside of us, we have, prepared, a series of petals cut out of the valves of the barnacle, and which we have taken care to classify in rows of increasing sizes. The first row, which will form the heart, comprises three small sheels, the second five, the third nine, and so on; but, in order to give a proper conformation to the flower, care must be taken to alternate by rows the direction of the valves, by now taking those of the right and then those of the left. The point is dipped into-La Nature. the gum, and the petals are inserted one by one in the wax support. The gum on drying fixes the petals very firmly. The whole skill of the florist consists in selecting the proper shells, and in the insertion of the petals, avoiding too great a symmetry. The flower is formed with wonderful rapidity. The stem is covered with a thin layer of cotton to give it the desired thickness, and is then covered spirally with a strip of green tissue paper. The cardboard base is covered with green paper, cut so as to imitate sepals, then the leaves are affixed to the stems, and, if need be, there is added a little stem, to which is gummed a white cone, carved from cuttlefish bone, and provided with paper sepals. This forms the extremity, and the flower and its bud are finished. The operation is the same for forming a chrysanthemum; but the petals here are imitated with the lances of the barnacle. If the flower possesses a disc, as in the daisy or the aster, there is employed either a coloured cardboard centre, such as may be found in the shops, or one that may be easily made by kneading a little bread into the desired form upon a brass wire hook. This is covered with gum and then dipped into the fine semoule, and coloured yellow with a little saffron or turmeric. The narrow valves of the barnacle, shaped with a file, are to be gummed beneath the disc, and will form the ray flowers (Fig. 2, A). The whole is consolidated with green paper, cut to resemble bracts. The manufacture of China asters will put the patience of the florist to a severe test. Flowers of this kind have been shown to us that were scarcely as large as a fifty-cent piece, and which yet contained nearly a thousand of these little shell plates. In order to form centres with projecting stamems, it is necessary to use a pencil of silk threads stiffened by gum, and the point of which, passed over starch paste, is sprinkled with grains of semoule made yellow with saffron or red with carmine. Another kind of shell much employed is the tooth shell (Dentalium tarentinum, Lam. Fig. 2, d). This is a sort of conical, slightly bent tube, of a pure white, or ring-streaked with yellow, which is usually found only in a rolled state. The tubes serve for the manufacture of all those flowers whose corolla expands at the extremity of an elongated calyx-such as the fuchsia, the honeysuckle, the primrose, the jasmin, &c. cliffs a small primrose with a brown corolla and Under the name of bear's ear, we find upon the white calyx which is quite easily imitated. A small white tooth shell will furnish the slender calyx. To the top of this is gummed, flatwise, a white shell in the form of a widened funnel (Calyptræa, Fig. 2, m), and to the edges of this are fixed in pairs those small brown opercula which close the orifice of the periwinkle. Small mussel shells with pretty violet tints, after having been carefully freed from all animal integuments by an immersion in hypochlorite of lime, will serve for making Canterbury bells, scabiouses, violets, and forget-me-nots, even. the sea-urchin, according to their colour, are The spines of employed for blue-bottles, resedas, scabiouses, &c. Commerce furnishes silk ribbons woven in the form of flat fringelets of a bronze green colour. ANALYSING FERTILISERS. THE following are the metals adopted by the I. Total Phosphoric Acid.-Weigh out 2grm. in 1. The molybdic method: 25 cubic centimètres of the solution are digested in a water bath at 65° C. from one to two hours, with an excess of molybdic solution. The precipitate is brought upon a filter, and washed with water containing a little molybdic solution. It is then dissolved in ammonia water, the solution nearly neutralised with hydrochloric acid, and magnesia mixture added slowly, with constant stirring. The precipitate is allowed to stand at least three hours, when it is filtered through a Gooch crucible, washed with dilute ammonia, ignited, and weighed. 2. The following method is occasionally employed when phosphates of iron and alumina are present in small quantities only: To 50 cubic centimètres of the hydrochloric acid solution add ammonia in slight excess. After standing a few minutes, acidify with acetic acid, and filter off the phosphates of iron and alumina, washing carefully of ammonia to precipitate all the lime; digest for several hours at a temperature below boiling, and filter through double filters which have previously been washed with oxalate of ammonia, washing of iron and alumina on the filter with warm dilute thoroughly with water. Dissolve the phosphates hydrochloric acid, and wash into a beaker containing a small quantity of powdered tartaric acid. When the latter has gone into solution, mix with with water. To the filtrate add sufficient oxalate acid is determined in an aliquot part of the solution as under total phosphoric acid. Insoluble phosphoric acid: Add 100 cubic centimètres of neutral ammonium citrate (sp.gr. 1.09) to the beaker in which the digestion with water has been made. Put in a water bath and heat to 65' C. Drop in the filter containing the residue from the above operation, and digest for thirty minutes, stirring every five minutes. Filter and wash thoroughly, using the suction-pump. Dry and burn. The ash is then treated as under total phosphoric acid. Reverted phosphoric acid: The sum of the soluble and insoluble subtracted from the total gives the reverted or citrate soluble phosphoric acid. Reagents: The reagents used in the estimation of phosphoric acid are prepared according to direc tions given in the Proceedings of the Association of Official Agricultural Chemists, 1889, pages 225 and 226. For ammonium citrate, 370grm. of citric acid are dissolved in 1,500 cubic centimètres of water, nearly neutralised with crushed carbonate of ammonia, heated to expel carbonic acid, exactly neutralised with ammonia, and brought to a specific gravity of 1.09. The molybdic solution is prepared by dissolving 100grm. of molybdic acid in 417 cubic centimètres of ammonium hydrate of specific gravity 0-96. Pour this solution into 1,250 cubic centimètres of nitric acid of specific gravity 120, and set in a warm place for several days, or until a portion heated to 40° C. deposits no yellow precipitate. The magnesia mixture is prepared by dissolving 110grm. of crystallised magnesium chloride and 280grm. of ammonia chloride in 700 cubic centimètres of ammonia of specific gravity 0.96, and bringing to a volume of two litres. 2. Methods of Determining Nitrogen. The Kjeldahl and soda-lime methods recommended by the Association of Official Agricultural Chemists, in their Proceedings, 1889, pages 218 to 221, are employed, with occasional control analyses by the absolute cupric oxide mode. test. two grms. of the material in a platinum crucible, of barium and allow it to stand for a few hours. Filter through a Gooch crucible, washing with alcohol, dry and weigh, or filter through paper, wash as before, dry and brush the potassium platinic hair brush, and weigh. If very impure, the double chloride upon a weighed watch-glass with a camel's salt is washed with the strong solution of ammonium chloride, saturated with potassium platinic chloride. -Massachusetts Agricultural Report. DE WORM-WHEEL TEETH.* RAUGHTSMEN and pattern-makers frequently experience difficulty in determining the correct form of the worm-wheel tooth. The textbooks on mechanism usually indicate the principles involved in making the drawing, without giving work. The problem is not difficult; but time and specific directions in regard to the details of the patience are required for the attainment of an accurate result. In order to make the constructionsshould take in their order, and, to avoid confusion clear, we explain the steps which the draughtsman deriving the form of the tooth of a wheel from of lines, a large number of illustrations are given. We begin by indicating a simple method of those of the rack with which it is to gear. Let line is tangent to the pitch circle of the wheel at Fig. 1 represent the teeth of a rack whose pitch phosphoric acid is precipitated with magnesia tooth of the wheel which is to work in the space the point o. In order to ascertain the form of the mixture, and treated as in 1. Soluble Phosphoric Acid.-Weigh out 2grm. a bed, proceed as follows:into a beaker, cover with 10 to 15 cubic centi- Let Fig. 2 represent a template abcd correspondmètres of water, and allow it to stand for fifteen ing to the space between the teeth of the rack, and minutes, stirring three times at equal intervals.f, the pitch line. Draw on the template the Decant the solution through a filter into a gradu- parallel lines 1, 2, 3, &c., &c., at equal distances and let it stand fifteen minutes more, stirring as distances equal to those between the lines 1, 2, 3, ated cylinder. Add another like quantity of water, apart, and perpendicular to ef Lay off on the pitch circle of the wheel (Fig. 3) before. Filter the solution into the cylinder, and wash the residue on the filter until the filtrate By FREDERIO R. HONEY, Ph.B., Instructor in Trinity amounts to 200 cubic centimètres. The phosphoric College. From the American Machinist. the filtrate from the oxalate of ammonia. The |