: maladies. The bark of the root of the Asclepias gigantea, as it appears in the bazars of lower India, is of a pale colour, and has a bitter, and somewhat nauseous and pungent taste: the natives consider it as al terative; also as a gentle stimulant, taken in decoction to the quantity of two table-spoonfuls twice daily and Rheede, in his Hortus Malabaricus, where the plant is mentioned under the appellation of Ericu, says, that a decoction of its root is given in intermittent fever, and in those swellings of the limbs which women sometimes have after confinement. The powder of the bark of the root of the asclepias gigantea, called in Bengal madár powder, has been highly extolled of late as a valuable remedy in lues venerea, leprosy, and cutaneous diseases in general. Mr. Playfair, in a paper already mentioned, and which may be seen in the first volume of the Edinburgh Medical Transactions, goes so far as to say that it is one of the most useful medicines hitherto derived from the vegetable kingdom; and it would seem, by an excellent paper on" Elephantiasis as it appears in Hindustan," by Mr. Robinson, that he also bears witness to its powerful effects as a deobstruent and sudorific, in almost all cutaneous eruptions; the dose of this powder is from three grains to ten."† M. IV. A description of a set of Balances made for the purpose of delicate weighing; illustrated by drawings. By Lieut. J. Braddock. EDITOR OF THE MADRAS JOURNAL OF LITERATURE & SCIENCE. Sir, I have the pleasure to send you a description and drawings of a set of balances which I made a few years ago for the purpose of delicate weighing. My object in constructing them being efficiency with simplicity of parts they are not so elaborately finished as delicate balances usually are, but they are fully adequate to all the purposes of the private experimentalist, who is not supposed to have his finer balances in continual daily use. 2. The mechanical principles of the balance are too well understood to require a detail of them. I shall therefore simply mention that the knife edge of the fulcrum and the points suspending the scale pans must lie in a right line; and that the centre of gravity of the beam must not be above this line or the beam will overset, nor must it be too much below the line, or the vibrations of the beam will be too rapid, and the delicacy of the balance will be diminished and impaired. 3. I have four balances for weighing all quantities from * See Hortus Malabaricus, part ii, page 55 + Transactions of the Royal Asiatic Society of Great Britain. Vol. I Page 300. one grain to ten thousand. They have one support and one glass case in common to them all: the beams not required are kept in a box fitting in at the back of the glass case, so that they are always at hand. Fig. 12 is a perspective sketch of the case with one of the balances mounted. The figure ,speaks for itself.-It has a glass slide to close the front, and the usual contrivances of an assay balance for reli eving the beam and scale pans, and for adjusting the level. 4. The most delicate balance that I have is used for weights not exceeding 10 or 20 grains. It is made simply of a piece of well seasoned, clean, straight grained fir; and figure 1 is a representation of it. The knife edge works on a plane of agate; it is made of steel and was tempered as a workman would say "dead hard," being afterwards very carefully sharpened on a hone, and examined by a microscope. The edge is a perfectly straight line, smooth, well defined, not wiry, not a sharp cutting edge but rather slightly round, so that it may be firm enough to withstand the wear and tear that may be required of it, and yet be nothing more than a line, presenting no resistance, but acted on when in the beam by the slightest weight. Figure 2 represents the fulcrum and the centre part of the beam of the real size: the brass a, is screwed down by the screws b, b having a plate of brass c, under them to prevent the heads Penetrating the wood. The beam d, is notched out for the fulcrum e, to lay in, and the brass a, very securely fixes it in its position, care being taken that the notch is made at a right angle, and that it is not too deep. The fulcrum should porject a little above the beam so that the securing brass a, may press firmly upon it. The points a, a, fig. 1 were put in at as nearly equal distances from the centre as could be measured by a pair of compasses; for I did not intend the beam to be a balance of perfect equipoise, knowing the extreme difficulty of adjustment to quantities so minute as th orth part of a grain. 5. Fig. 3, shews one end of this balance of the real size. The point a, is a piece of hardened steel wire with a screw on it, screwing up tight through the wood of the beam b, and The point is being further secured by the tightening nut c. extremely fine and sharp, but carefully made, and proved or tested by pressing it upon a piece of wood to ascertain that it neither bent, nor broke; being afterwards examined by the microscope. The wire d, is the pointer, the point of it being a continuation of the right line of the fulcrum and the points of suspension for the scale pans. The end of this wire entering the beam was hammered flat, a slit was cut down the end of the beam, and the wire thrust in and tied securely with a piece of waxed silk thread as at g. 6. The scale pans of this balance are supported in the simplest manner I could devise. The crank piece e, fig. 3. is a piece of common brass wire flattened on the top, hammer hardened and polished underneath where it rests on the beam point a. This crank piece has a hook or hole at the bottom i. e. at f, and another piece of brass wire fig. 4. hooks on it, the lower end of this wire fig. 4. being bent at right angles into a triangular shape for the purpose of supporting the scale pans, which are small thin dishes one inch in diameter.The ball over the fulcrum f, Fig. 2. is common to all the balances, i. e. each balance has one; it is for the purpose of raising or lowering the centre of gravity, and the wire g, is for the purpose of adjusting the equilibrium of the balance before it is used. 7. The sensibility of this balance is very great, in fact so much so, that it is extremely difficult and tiresome to weigh with it. When 20 grains are in each scale the Tdth part of a grain occasions the pointer to move over 3 divisions of the index, which is graduated in 10ths of an inch; supposing with 20 grains in each scale the index points at nonius, or nothing, the addition of Tdth of a grain causes the pointer to move over a space of nths of an inch, so that the balance indicates decisively to part of a grain which causes the pointer to move over a division or of an inch, a quantity quite large enough to produce an indication that may be depended on. In fact half that quantity or dth part of a grain may be estimated, but all who know the difficulties of such minute weighing are aware that such statements appear much finer and more scientific on paper than they are to be depended on in practice. 8. A balance like this must be used with the utmost possible care, not as I once saw a gentleman use an assay balance, giving it a good hearty shake "because its indications were sluggish." The least accident deranges so delicate an instrument; the slightest breath of air, a particle of dust, or unskilful management. The difficulty in delicate weighing is to make a balance always agree with itself, which it will not do unless it is in perfect order, and unless it is under the sole care of one who is completely master of its peculiarities. Few practical men who have a good balance like another to use it. 9. I must add that the way to use this balance is this: suppose you wish to ascertain the accuracy of a given weight. Place a known accurate weight in the right hand scale, and equipoise it by counterweights in the other. When perfectly equipoised, take it out and put in the weight you wish to verify, then if on the second trial an equipoise is produced, the two weights are equal. Or if you wish to ascertain the exact weight of any small substance, place it in one scale and balance it by counterpoise weights in the other: remove it and by real weights produce an equipoise and the true weight results. This is in fact the only accurate method of weighing, for the best balances are seldom perfectly correct, particularly after they have been in use for some time.---It is very difficult to adjust delicate balances so as to be perfect equipoises, though the adjustment may be made so very near the truth as to be a matter of no consequence for any ordinary practical purpose. 10. My second balance weighs any quantity not exceeding 200 grains and indicates to the 7th part of a grain. Figs. 5, and 6, represent the central portion, and the index end of this balance of the full size. The length of the beam is the same as in Fig. 1.-The general construction is the same in principle as the balance just described, but being designed for more frequent use the beam is made of steel, which by means of linseed oil put on it and burned off over a fire was blackened and covered with a sort of varnish that prevents its rusting. The fulcrum is a piece of square steel wire made dead hard by heating it cherry red, and plunging it into cold water. Then as in the former case working it to a proper edge on the hone. In fig. 5, a, is a piece of brass screwed down upon the beam b, securing the fulcrum c, which is further fastened by the bottom end of the upright wire d, entering a hole made to receive it on the upper part of the fulcrum. This prevents side motion, the wire being screwed through the brass a. ---The ends of the beam fig. 6, are tipped with brass, and the point a, slides in a small groove made to receive it, and is secured by the tightening nut b. The thick end of the pointer c is screwed through the end of the brass d, and abuts against the point a,affording the means of adjustment by thrusting the point a, towards the centre of the beam:-e is a tightening nut to make the pointer c, secure.-A plain piece of wire with a screw on it, is used also at the other end of the beam for the same purpose.—I shall presently state the method I used for adjusting the beam to make it an equipoise. 11. The scale pans of this balance are suspended by a loop, figure 7, where a, is a small steel screw passing through the top of the loop, having a shallow cup or dishing at the bottom to prevent its sliding off the point, which with the end of the beam is shewn inside the loop. This small concavity is finely polished, and is intended by being concave simply to secure the loop from wandering, or slipping off the point but it does not at all interfere with the delicacy or sensibility of the balance, which it might do were it not carefully formed, and made as shallow as possible with reference to the use required. The wire bent into the figure of an 8 with the three lines attached to it represent the manner in which the scale pans are secured, the lines being merely silk thread.—This balance is a very good instrument, and its indications are satisfactory and may be depended on with from 100 to 200 grains in each scale to the part of the weight. th 12. To make this balance an equipoise I proceeded thus. I adjusted the points in the beam as nearly as I possibly could to equidistances from the fulcrum, and then made the beam balance, or point to nonius on the index.-The scale pans with the loops complete were then made perfectly equal in weight. They were then attached to the beam and two perfectly equal weights of 100 grains each were put into the pans, one in each pan, and the balance tried. The end that |