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The photographic news
- Bandzählung
- 27.1883
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- 1883
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- Hochschule für Grafik und Buchkunst Leipzig
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The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
- Ausgabe No. 1270, January 5, 1883 1
- Ausgabe No. 1271, January 12, 1883 17
- Ausgabe No. 1272, January 19, 1883 33
- Ausgabe No. 1273, January 26, 1883 49
- Ausgabe No. 1274, February 2, 1883 65
- Ausgabe No. 1275, February 9, 1883 81
- Ausgabe No. 1276, February 16, 1883 97
- Ausgabe No. 1277, February 23, 1883 113
- Ausgabe No. 1278, March 2, 1883 129
- Ausgabe No. 1279, March 9, 1883 145
- Ausgabe No. 1280, March 16, 1883 161
- Ausgabe No. 1281, March 22, 1883 177
- Ausgabe No. 1282, March 30, 1883 193
- Ausgabe No. 1283, April 6, 1883 209
- Ausgabe No. 1284, April 13, 1883 225
- Ausgabe No. 1285, April 20, 1883 241
- Ausgabe No. 1286, April 27, 1883 257
- Ausgabe No. 1287, May 4, 1883 273
- Ausgabe No. 1288, May 11, 1883 289
- Ausgabe No. 1289, May 18, 1883 305
- Ausgabe No. 1290, May 25, 1883 321
- Ausgabe No. 1291, June 1, 1883 337
- Ausgabe No. 1292, June 8, 1883 353
- Ausgabe No. 1293, June 15, 1883 369
- Ausgabe No. 1294, June 22, 1883 385
- Ausgabe No. 1295, June 29, 1883 401
- Ausgabe No. 1296, July 6, 1883 417
- Ausgabe No. 1297, July 13, 1883 433
- Ausgabe No. 1298, July 20, 1883 449
- Ausgabe No. 1299, July 27, 1883 465
- Ausgabe No. 1300, August 3, 1883 481
- Ausgabe No. 1301, August 10, 1883 497
- Ausgabe No. 1302, August 17, 1883 513
- Ausgabe No. 1303, August 24, 1883 529
- Ausgabe No. 1304, August 31, 1883 545
- Ausgabe No. 1305, September 7, 1883 561
- Ausgabe No. 1306, September 14, 1883 577
- Ausgabe No. 1307, September 21, 1883 593
- Ausgabe No. 1308, September 28, 1883 609
- Ausgabe No. 1309, October 5, 1883 625
- Ausgabe No. 1310, October 12, 1883 641
- Ausgabe No. 1311, October 19, 1883 657
- Ausgabe No. 1312, October 26, 1883 673
- Ausgabe No. 1313, November 2, 1883 689
- Ausgabe No. 1314, November 9, 1883 705
- Ausgabe No. 1315, November 16, 1883 721
- Ausgabe No. 1316, November 23, 1883 737
- Ausgabe No. 1317, November 30, 1883 753
- Ausgabe No. 1318, December 7, 1883 769
- Ausgabe No. 1319, December 14, 1883 785
- Ausgabe No. 1320, December 21, 1883 801
- Ausgabe No. 1321, December 28, 1883 817
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274 THE PHOTOGRAPHIC NEWS. [May 4, 1883. exposed four, or even six times as long as the rapid, they still developed more slowly. Here we had a distinct observation; but the effect pro duced might be due to one or two causes. It might be due to the difference in time taken for dryiug, or to difference in the temperature of drying. To determine which was the factor actually bringing about the result, we coated a few plates, and placed them in a fairly air-tight box with some thoroughly dried calcium chloride, but did not raise the temperature. We do not know exactly how long these plates took to dry, but as they were coated over night, and were dry in the morning—that is, after ten hours—it is probable that they took not very much longer than those which were dried at the high temperature. They were, however, as sensitive as those which had taken two days to dry, and developed as quickly. A still more remarkable experiment, and which completely corroborates the last in showing that the influencing factor is the temperature, and not the time of drying, was as follows ;— Several plates were coated and left drying without artificial heat for about twenty hours. At the end of that time, probably about half the area of each plate was dry, a patch in the centre remaining wet. The temperature was now very greatly raised, to somewhat over 80° Fah. The plates on testing, when dry, all showed an insensitive patch in the centre. This patch showed all the character istics of the plates, which had been dried from the beginning at a high temperature; that is, they were insensitive, and beyond that took a very long time to show any image at all, and that although they were the portions of the plate which had taken longest to dry. ■ This last result somewhat puzzled us, as we had at times before noticed that the portion of a plate which had taken longest to dry, even if the temperature had been somewhat raised during the process, was more sensitive than the surrounding portion. On reflection it recurred to us that these observations had been made in the case of slow plates. On the force of this, we repeated the experiments which we had just described with a slow emulsion, the first having been performed with a very rapid one. We now found that we got very much less marked differences in result. The plates which were dried at the highest possible temperature were very little slower than those dried without artificial heat. The conclusion which we draw from the experiments described is, that in the case of very rapid emulsions the silver bromide is in a form in which its sensitiveness is very readily modified by pressure, or some such influence, and that the sensitiveness may be altered to a very marked degree by the mere temperature at which drying of the plates is performed. Between limits quite likely to occur in practice—that is, between the temperatures of about 50° and 70° Fah.—we found variations of sensitiveness as great as two or three to one produced. We find also that not only is the sensitiveness modified, but that the quality of the plate is changed ; the plate dried at a low temperature developing much more rapidly than that at a high. In fact, it would appear that far too little attention has been given to the subject of drying plates. We are given formulas which, we are told, will give plates of such and such rapidity, and it is not even taken into account that the process of drying the plates may produce as great a variation as three to one. In this variation we undoubtedly have some explanation of the extraordinarily different results which different experimenters get with the same formula. Of course the lesson which our experiments teach us is, that the lower a temperature we can dry our plates at, the better. We may say, however, that we did not observe any slowing effect till a temperature of about 60° Fah. was reached. Still, we would say, to make it a rule not to use artificial heat at all, except in very cold weather. There is no need for it if a plentiful current of fairly dry air be used. This can only be brought about by having very large air passages to supply the necessary ventilation to the drying room or cupboard. THE EXPLOSIVE SUBSTANCES ACT, 1883. The seizure of an enormous weight of nitro-glycerine in the heart of the metropolis, following quickly after the Parliament Street explosion, has thoroughly aroused the British public, and Londoners in particular, to an appre ciation of the awful danger to which we have been exposed, and which is, let us hope, safely past. The mystery is being fathomed, and evidence is being brought out, thanks to the energy of the police, which proves how deeply rooted is this secret organization, which seems to aim at wanton destruction of property, and murder of innocent people. Men who dabble in science are often sneered at by those who do not pretend to know anything about it, and who lose no opportunity to urge that their ignorance is a virtue; but how would it have been by this time if the Birmingham police officer and his friend who saw the tins of glycerine going into the shop in Ledsam Street, had known nothing of chemistry ? Probably thousands of pounds of our property would have been demolished, and, may be, many lives lost, had these dynamite miscreants had the opportunity of distributing and exploding their infernal luggage. The Birmingham police officer has stated that he had been learning chemistry and photo graphy, and undoubtedly but for this fact, London would have been ere this startled by the crash of one of the most desperate conspiracies of modern times. With an unanimity which is quite assuring, the Govern ment have framed and succeeded in passing through both houses of Parliament, in a few hours, a measure of great importance, more than justified, probably by the exigen- cies of the times. The principal clauses of the Bill deal with the penalty incurred by those who dare to engage in this class of hazardous crime, the greatest punishment under the new Act being penal servitude for life, and none too much either ; but the Bill deals with the trafficking in or possession of any of the materials for making explosives as well as of explosives themselves; and under date of the 18th April, the Home Secretary has issued a “ memo randum " drawn up by the chief inspector of explosives, and addressed to the clerks of all local authorities, and which was published in the newspapers of the 19 th. The essence of the communication appears to lie in the foot note of which we give a reproduction: — “ Memo.—Independently of the purchase of explosives (such as dynamite, blasting gelatine, gun-cotton, tonite, potentite, and detonators), specially adapted for blasting, and therefore generally available for destructive purposes, by persons who may not be reasonably supposed to require the same for industrial objects, suspicion should attach to the acquisition in notable quantities of all or any of the materials adapted for the making of explosives, when the person seeking to purchase the same is unknown to the seller, or is not known to require such materials for trade pur poses or other legitimate use. Among the substances which fall within this category, may be specially enumerated the following : nitric acid, sulphuric acid (especially in their more concentrated forms), glycerine, saltpetre, Chili salt petre (nitrate of sodium), chlorates (especially chlorate of potash), picrates, picric acid, phosphorus, iodine, metallic mercury, nitrate of mercury (even in comparatively small quantities), orpiment.” We give this exactly in the form in which it has been published, because the moment we read it, we were struck with the conviction that this Act may prove exceedingly troublesome to perfectly honourable, upright, and righteous people. At the present time we have somewhere about our
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