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July 31, 1863.] THE PHOTOGRAPHIC NEWS. 369 rain-drops have left their marks, and the shell-fish the grooves in which they crawled, and the wading-birds the divergent lines of their foot-prints,—tears, cares, griefs, once vanishing as impressions from the sand, now fixed as the vestiges in the sand-stone. Attitudes, dresses, features, hands, feet, betray the social grade of the candidates for portraiture. The picture tolls no lie about them. There is no use in their putting on airs ; the make-believe gentleman and lady cannot look like the genuine article. Mediocrity shows itself for what it is worth, no matter what temporary name it may have acquired. Ill-temper cannot hide itself under the simper of assumed amiability. The queru lousness of incompetent complaining natures confesses itself almost as much as in the tones of the voice. The anxiety which strives to smooth its forehead cannot get rid of the tell tale furrow. The weakness which belongs to the infirm of purpose and vacuous of thought is hardly to be disguised, even though the moustache is allowed to hide the centre of expression. All parts of a face, doubtless, have their fixed relations to each other and to the character of the person to whom the face belongs. But there is one feature, and especially one part of that feature, which, more than any other facial sign, reveals the nature of the individual. The feature is the month, and the portion of it referred to is the corner. A circle of half an inch radius, having its centre at the junction of the two lips, will include the chief focus of expression. This will be easily understood, if we reflect that hero is the point where more muscles of expression converge than at any other. From above comes the elevator of the angle of the mouth; from the region of the cheek-bone slant downwards the two xygmnatics, which carry the angle outwards and upwards; from behind comes the buccinator, or trumpeter's muscle, which simply widens the mouth by drawing the corners straight out ward ; from below, the depressor of the angle; not to add a seventh, sometimes well marked,—the “ laughing muscle ” of Santorini. Within the narrow circle where those muscles meet the ring of muscular fibres surrounding the mouth the battles of the soul record their varying fortunes and results. This is the “ noeud vital ”—to borrow Fleuron’s expression with reference to a nervous centre,—the vital knot of expression. Hero we may read the victories and defeats, the force, the weak ness, the hardness, the sweetness of a character. Here is the nest of that feeble fowl, self-consciousness, whoso brood strays at large over all the features. If you wish to see the very look your friend wore when his portrait was taken, let not the finishing artist’s pencil intrude within the circle of the vital knot of expression. (To be continued.) • Corresyondence. FOREIGN SCIENCE. [FzoM OUR SPEOIAL OOXNESPONDEST.1 Paris, 29th July, 1863. Mn. HAnT, of London, at the recent meeting of our Society, exhibited a positive printing frame, in which, by introducing a dissected screen, a positive proof can be taken from different negatives. The principal object kept in view in constructing this apparatus is the facilitating the adjustment of the nega tives and screens employed in taking positives from several negatives. The small model exhibited has been made to obtain proofs upon tinted grounds, intended to bo retouched, an operation that succeeds very well with proofs of small dimensions. The following is the principle of construction :—Take a piece of very dry wood, of such size that it exceeds the dimensions of the largest proofs to be taken by 2} to 3 inches on each side. Upon the middle of this board is placed a thick sheet of caoutchouc, selected for its eminently elastic qualities; this sheet must be a little larger than the proof to be printed in the frame. At the extremity of this sheet a rod of the same thickness is placed, which, pressing against it by means of a spring, maintains the positive paper in a fixed position. Over the whole a hinged frame is adjusted, made to move horizontally in every direction, and so arranged that while the hinged extremity is fixed, the greater portion of the frame may be raised to permit the examination of the progress of the picture, without fear of displacing the negative, or the screen which covers a portion of the positive. This frame must be solid ; it carries either one or two bars, for the purpose of keeping the glass plate or negative in the desired position in relation to the prepared surfaci. When the printing necessitates the employment of many negatives, it is preferable, in the inventor’s opinion, to transfer the latter to gelatine or other transparent support, and to adjust them on the plate as they are adjusted in the frame, nearly in the desired position, and to arrange them afterwards in a manner conformably to the portions already printed. M. Frangois Pierson has invented a machine for beating albumen, which he has for a long time employed in pre paring paper. The metal dasher- with which the eggs are beaten, is moved mechanically with great rapidity, by means of a fly-wheel, which turns freely, and a system of eccentrics. The vessel containing, the albumen turns upon itself con tinually during the operation. By means of this machine we can beat into froth, in the space of five minutes, as many eggs as forty minutes’ fatiguing labour would not suffice to bring to the same condition. M. Hulot exhibited to the society his method of splitting and parchmentizing paper. The paper is im mersed in sulphuric acid diluted with 20 per cent, of water, and allowed to remain a given time, according to the nature and thickness of the paper which is afterwards rinsed in water. Thus treated, the paper splits with great facility, and the sulphuric acid having closed the pores, it has much more compactness, gaining in consistency while becoming thinner. It is remarkable that the colour does not change. This treatment may bo applied to negative proofs only, as M. Adolphe Martin observes that this paper, after being parchmentized, cannot be waxed. M. Lucy has communicated his method of the chemical colouration of proofs in the toning bath. The tints, which produce a remarkable effect in the flesh and drapery, are produced by a combination with the chloride, which enters into the preparation of the paper with a metallic chloride, which the operator applies, before immersion in the toning bath, to those parts of the picture he wishes-to colour. The reaction then takes place, and the hue is according to the salt employed. The alkaline chlorides are the best. Dr. Schnauss has published in the Photographisches Archiv, an analysis of the metallic bromo-iodo-cyanide salt, to pre pare and sensitize the instantaneous collodion composed by M. Mazac. This preparation contains iodine, bromine, and the metals ammonium and cadmium, but no cyanide. To prepare a coilodion identical with that of M. Mazac’s, Dr. Schnauss gives the following formula:— Iodide of ammonium 4 parts. Iodide of cadmium ... ... 2 „ Bromide of cadmium 1 „ The sulphate of iron and ammonium has become, in Germany, the source of a very censurable industry. We read in the principal newspapers advertisements inviting photographers to send ten dollars, for which they will re ceive the formula of a new developer for very vigorous and delicate negatives without intensifying. One of these advertisers impudently asserts that “ ho is honoured with a medal from the Great Exhibition.” Upon opening the letter- containing this precious formula, we find sulphate of iron and ammonium recommended. A photographer ad dresses the following letter to us on this subject: “ X is a cheat; for the ten dollars he sends the following formula :— Iodide of potassium ... 150 grains. Bromide of cadmium ... 65 „ Iodide of cadmium ... ... 85 „ Collodion, composed of equal parts of ether and alcohol 31 ounces.