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418 THE PHOTOGRAPHIC NEWS. [August 29, 1862 gradual conversion of one of these forms into the other, and the other members could easily be added. We have seen that while the electrical brush is charac terised by the annular form, electricity of higher tension generates star-like figures, the rays being larger in propor tion to the tension up to a certain point. Now the constant occurrence of a combination of these two forms, in the pho tographs of bright sparks, points out, I think, clearly, that these sparks consist also of more than one discharge ; more over, the ring, where it cuts the rays of the star, can often be traced under them, as though superposition had taken place. Again, when the bright spark travels some distance the ring is generally not symmetrically placed, as though the discharge producing it had followed a slightly different path. Indications arc constantly observed which lead to the idea that even the star itself is produced by the overlapping of two stars, having rays of different size and different inten sity. The wet collodion film offers, of course, a certain amount of resistance to the passage of electricity over its surface, and thus furnishes uo with the different indications above described. Finally, as the researches of Reiss, Kirchhoff, Helmholtz, and Feddersen, have shown that the electrical discharge is oscillatory and wave-like, I am the more inclined to regard these photographic figures as produced by a series of con secutive discharges of different intensity. Before passing on to the next point of interest, I will allude to a curious modification which the positive partial spark undergoes if the machine be turned rapidly, so that a large number of them fall quickly on the same spot: see yfig- 2. Many of the partial sparks are arranged rapidly around the point under the brass ball, the pointed portion being turned outward.—A merican Journal of Science and Art. Coxrespondentt, FOREIGN SCIENCE. [FROM our special CORRESPOXDENT.] Paris, 21th August, 1862. From the multitude of suggestions for new or revised for- mul in the various photographic processes, a sanguine person might conclude that we are fast approaching the goal of perfection and infallibility. If in a multitude of counsellors there is much wisdom, then photography is sin gularly fortunate, for surely no subject that ever engaged the mind of man can show a more formidable array of coun sellors pregnant with experience and wisdom. It would seem to be very easy to take rank as an inventor or dis coverer in photography, honey or treacle may serve your turn, but unhappily the glory thus acquired is very short lived; and it behoves the ruling genius of the hour to make the most of his opportunity, for raspberry-vinegar may be looming in the future, and quickly terminate honey or treacle’s existence. I see by our Journals that the resin benzoin has been brought into action by an ingenious operator. He puts it into his collodion, and he puts it on to his positive printing paper, with what result I cannot yet inform you, as I have not had leisure to repeat his experiments; but as there may be something in it, I proceed to quote his formula:. First, as to the benzoinized collodion, take Ether 100 parts Alcohol ... ... ... ••• 50 „ Pyroxyline ... 1 „ Iodide of cadmium ... ••• O u ,, Iodide of ammonium ... ••• 0 5 „ Bromide of ammonium 01 „ Bromide of cadmium ... ... 01 » Chloride of cadmium ... ... 03 , Benzoin ... ... 04 „ His sensitizing bath is composed of Water 100 parts Nitrate of silver ... 8 „ Acetic acid ... ... ... 10 „ The plate being sensitized, it must be well wasted qad dried. It will be nearly twelve hours before the plate becomes dry. The exposure required is a little less than that required for the Taupenot process. Four minutes for a stereoscoPl. plate, 5 to 10 for a plate 10 by 12. Upon removal from the camera the plate is immersed in a dish full of water. The water employed for washing the plate will answer. When the film is thoroughly moistened, the picture is developed with pyrogallic acid, just as with wet collodion. Thedeve lopment must not occupy more than five minutes. The fixing is performed with hyposulphite of soda. Any wd collodion that gives good negatives may be employed in a dr state, by adding 0-27 of benzoin to 100 of collodion. This collodion succeeds very well when employed in the wet state; it yields very intense blacks. The method of printing positives does not differ in prin ciple from the ordinary process with chloride of silver, bu only in detail. The paper is first prepared with the follot ing solution, in which the paper may be wholly immersed or floated. Alcohol at 36° 100 parts Benzoin ... ... ... ... 10 „ Chloride of cadmium ... ... 5 „ It is more expeditious to immerse the paper than to flost it. The sheets are hung to drain and dry in the usual manner, and they dry very rapidly ; they may be dried by 5 fire if time presses. The improvement effected by the benzoin is in closing the pores of the paper; air and moisture cannot penetrate the proof, which is thus protected from the chief, if not the only cause of its destruction. The benzoin also gives aglosi to the surface of the paper, but not so much as is given by albumen. The paper thus prepared may be preserved for a long time: it is sensitized in the following bath, as with albu- menized paper. Water ... ... lOOparts Nitrate of silver ... 15 „ In printing, this paper requires less exposure under th* negative than albumenized paper. Another operator recommends the following variations i the tannin process, as yielding the best results. Solution of Tannin— Distilled water ... ... ... 500 parts Tannic acid 4 „ Alcohol rect 25 „ Dissolve and filter. The sensitizing bath consists of Water ... ... ... ... 1000 parts Nitrate of silver ... ... ... 00 „ Acetic acid ... ... ... 10 „ The same collodion as employed in the wet process may be employed ; if a little bromidized it will be preferable. Manipulation—After the plate is sensitized, it is carefull! washed in distilled water, allowed to drain for a moment and then the tannin solution poured on. It is dried out 01 the reach of dust, and the edges of the plate covered with picture varnish. , 'The exposure in the camera is 10 to 15 times longer than when operating with wet collodion; but by warming the plate before the development, the exposure may be greatly diminished. Development solution— Water Pyrogallic acid Acetic acid 500 parts 5 „ 50 „ AUGus Re plate kid is po filing a tent. Th M. 1 itit n this 3 “‘uly PRI Sir,—I vhich onl four fas 7 freely 1 ’further < Btat brie lly into Mhithe Nfy and Bere spol Sposed t ‘-'truss tl Ake a 1 "Bes pei 'Bessary Uyeate Miment kd if, I * an ’’bouts w Comm "Btmen Piotogra "tfind N, e a 'tally t bibqte, Sto tlers; te 'the Bleven Bbstanei retai, s? 2 Bti 6 dis! SV 2abu on vBnar w I "hent 1! Nqb)