Volltext Seite (XML)
November 7, 1862.] THE PHOTOGRAPHIC NEWS. 537 Fourthly, and lastly, there is Au Cl. This is the state in which Nos. 2 and 3 will become if a larger quantity of soda is added than is enough to destroy the free acid, and one equi valent more. It also is produced under the same circumstances when the prints are boiled in the bath, to try and make them tone quicker. Many operators are surprised to find the bath suddenly stop, when they know there ought to be plenty of gold in it, the solution when in this state; becomes quite colourless, and is so inert that it may almost be said to be devoid of toning properties altogether. Now for some practical conclusions from the above : the first thing would be to find the amount of free acid in the gold; but the only method I know of to do this, is a very uncertain one in the hands of inexperienced persons: it is to add soda carb, to the gold, until test-paper is no longer strongly reddened, but the difficulty of seeing the difference between the acid of the hydrochloric, and the reddening of the free carbonic, will lead some to add a much larger amount than will be correct. I can therefore only recommend the following: lay in a stock of gold so as to save trying often, keep it in solution, say 8 or 10 grains to the ounce, for use; then take four or five beaker glasses—clean jam pots will do as well—put into each, say } ounce of gold solution, and into the first } grain of soda per grain of gold ; second, 1 grain; third, 2 grains; fourth, 4 grains; fifth, 6 grains; pour on each 4 or 5 ounces of boiling water, which will, in ten minutes or so, bring on a perfect decomposition of the gold. Then dilute to the proper extent with water, and im merse a few prints in each, the results will probably be as follows : No. 1, prints reduced, bad colour, horridly mealy ; No. 2, little better; No. 3, intense black and white, rather increased than reduced in strength, toned rapidly, and do not change in the hypo. This solution will tone from two to three sheets to the grain of gold before it is exhausted, and will not require to be heated to tone quick enough in any state of weather up to this date, end of October. No. 4, the solution has become first, colourless, then slightly opaque, a greenish deposit on the side of the glass, and when prints are immersed, hardly any toned action at all. I do not say that these preparations will act exactly with all gold in the order indicated, but they can be pro duced most certainly with every sample of gold that may be obtained.* I can only say in conclusion, let every one work it out for himself, and if I have advanced anything that may aid the thoughtful printer in his endeavours, I shall be only too gratified, and would wish him every success. 4 9 hotographit U onrist. A PHOTOGRAPHIC TRIP TO THE PITCH LAKE, TRINIDAD.t BY W. TUCKER. Next morning we returned by the same road, and found everything as we had left them the day before, safe and dry, although it had rained considerably during the night. Hills close up this side of the lake, and on the one over which we passed a very pretty view of the lake and its islands is obtained through a vista of trees. The depth of the pitch is probably less on this than on the northern or La Brea side. Patches of high grass, and islands covered with trees, occur frequently, and considerably relieves the monotonous appearance. After a refreshing bath in one of the larger fissures, we made our way to the centre of the lake, where the greatest uninterrupted mass of pitch is collected. The natives call it pitch-pot on account of its round form, resembling a giant iron cooking-pot, and from the bubbling noise in the soft pitch in several parts. To me it resembled an immense black pie-crust. The Pitch Lake is highest on * I wonldalso add, that the gold in the state of Au Cl is much more perma nent than is usually imagined ; I have kept it undiluted for a week, and no doubt it would keep much longer ; it is excess of alkali that causes it to go on decomposing, and then to precipitate the gold. t Continued from p. 513. this spot, and the rain water finds its level in the crevices of the lower sides. All attempts to ascertain the depth of the lake have been unsuccessful; a hole that had been cut out by Mr. Stollmeyer, large enough to allow of twelve men working inside, closed up in a couple of days, and before all the material cut out with wooden axes, could be carted away. The surrounding layers or waves of pitch press towards any disturbance of its equilibrium, and no practical purposes could be served by digging lower under increasing diffi culties. The experiment, however, is sufficient to prove that millions of tons of asphalt are here attainable. Near the pitch-pot is found in several places the soft or semi-liquid pitch of the consistence of stiff dough, oozing up from beneath—the actual oozing is not observable, but in several places near the edge there is a bubbling of muddy water and gas—giving forth a disagreeable odour. The negroes said that several cattle had disappeared in the soft pitch, and some time after again reappeared floating in the gulf. The water oozing up is strongly impregnated with salt, and mixed with grey mud ; and certainly from its taste, and the colour of the mud, strongly leads to the belief of its connec tion with the sea. The semi-fluid pitch, when cut, resembles fermented dough ; and water can easily be squeezed from it by pressure from the hand. It is not at all adhesive, and will bear passing over it at a quick pace in the wet season. In no part is it deeper than the fissures, which, too, suffi ciently proves the absurdity of the idea of any large animal disappearing in it. In fissures formed near the pitch-pot, the soft pitch generally replaces the rain water, which it forces out from the bottom, and retains the base of hard pitch. This soft pitch requires a long exposure to the sun, in order to evaporate the large portion of water with which it is mixed, before it will solidify and combine with the hard pitch of the lake ; until then it lies on the surface as a flake,’ in the form of the fissure, and may be removed near the edges, curled up and rolled without much soiling the fingers. Near were several of the filled fissures, in which the pitch was quite hard. In several parts of the lake, but par ticularly near this spot, severalparts:of logs and branches of trees were above the surface. I examined several, and found them in different stageebf transformation ; some were merely saturated with petroleum, others were of the same bituminous consistency as the pitch, but more brittle, and retaining all the fibrous appearance of wood. Others were traceable on the surface of the lake only from the fibrous appearance of the log, having, as it were, become fused into the main body of the lake. As the morning was showery I did not attempt to photo graph. At mid-day, however, the sun shone out with a true tropical glow, and soon dispelled the icy appearance given to the surface by the rain, and resumed its usual dull black. Having taken off my boots a little time before, I was glad enough now to seek their protection from the heated surface, which rendered the manipulation of the next two views a matter of great difficulty, from the intense heat in the tent, combined with what I cannot better de scribe than as hot bricks under my feet. I was glad to lean on the edge of my tent and relieve the burning sensation by lifting both my feet at times during the process, which caused the tent so to sink on this side as to require a fresh removal and re-levelling (for this reason, that I made use of the top in place of a tripod stand). By perseverance, how ever, I obtained three views. In the meantime, the surface of the lake had become so hot, that standing in one position for twenty seconds caused a burning, blistering sensation in the soles of the feet. We now, and to my relief, moved over to the southern side, which is, perhaps, the most interesting portion of the lake, being bounded by beautiful Moriche palms, which are reflected in the rain-water between the pitch deposits in as clear and sharply defined a manner as in a mirror. Nowhere in Trinidad is the Moriche palm found in such numbers, and in such perfection as in this particular place, where they grow wild. No visitor to the Bitch Lake should omit seeing this jewel of Nature ; but
