628 



PHOTOGRAPHIC PROCESS. 



dezvous for all the American whalers in the 

 South Pacific. It is the seaport of Piura, from 

 which it is distant about forty miles. It ex- 

 ports large quantities of raw India-rubber, 

 Peruvian bark, cocoa, drugs and dyes, and 

 quite a respectable amount of cotton of a very 

 fine quality. The road will be completed in 

 six months. The next in importance is the 

 road to Trujillo. The railway is to run from 

 the seaport of Trujillo to Huanchaco, and 

 will aid very materially in the development 

 of the resources of several very wealthy prov- 

 inces. It will traverse the fertile valleys of 

 Chicama, Santa Catalina, and Viza. The val- 

 ley of Ohicama alone contains 125,000 acres of 

 cultivated land. 



A very severe earthquake was felt at Lima 

 on the night of the 21st of August, at 8.32 

 o'clock. The undulations were from north- 

 west to southeast, and were of twenty seconds' 

 duration. Great alarm was created, and al- 

 most the entire population rushed into the 

 streets. The shock was very severe at Cerro 

 Azul and Pisco, on the coast. The sea, which 

 previously had become unusually placid, sud- 

 denly became very rough and tumultuous, 

 and continued so throughout the next day. 

 No tidal wave was experienced, though the 

 surf rolled in upon the coast with great vio- 

 lence. 



PHOTOGRAPHIC PROCESS, A NEW. 

 An entirely novel method of photographic 

 printing has just been discovered by M. Mer- 

 get, Professor of Physics at the Faculte des 

 Sciences of Lyons. The principal points dis- 

 covered by M. Merget may be thus summarized : 



1. The vaporization of mercury is a contin- 

 uous phenomenon, that is to say, the metal 

 emits vapor at all times, even at a very low 

 temperature, and when in a solidified form. 



2. Mercury-vapor may be condensed upon 

 certain substances, such as carbon, platinum, 

 etc., without these latter being chemically af- 

 fected. 



3. Mercury-vapor will pass with exceeding 

 facility through porous bodies, such as wood, 

 porcelain, etc. 



4. The salts of all precious metals when in 

 solution are very sensitive to the action of 

 mercury-vapor, which has the effect of rapidly 

 reducing them. 



The most sensitive to mercury of the pre- 

 cious-metal salts are nitrate of silver and the 

 soluble chlorides of gold, palladium, and irid- 

 ium, and paper prepared with any of these 

 forms at once a most delicate test for the vola- 

 tile metal ; but the solutions must contain 

 some hygrometric body to prevent complete 

 desiccation, so that the surface coated with 

 them will always remain in a moist condition. 

 To demonstrate how exceedingly sensitive this 

 test-paper is to mercury, we may state that a 

 section of wood, exposed to mercury-vapors 

 and afterward pressed in contact with a sheet 

 of sensitive paper, prints off upon the surface 

 all the rings and markings it possesses, the 



mercury being deposited in the pores of the 

 wood in a more or less condensed form. 



In the event of nitrate of silver being used 

 for preparing the paper, it is necessary, obvi- 

 ously, to exclude the light, as otherwise a 

 reducing action will be already set up by solar 

 means alone ; but with the salts of palladium 

 or platinum no such action need be feared. 

 According to the kind of metallic salt em- 

 ployed, so the tint of the impression varies ; 

 but in most cases an intense black may be 

 obtained where the action has proceeded far 

 enough. 



Having described M. Merget's discoveries 

 thus far, it is easy to guess how that gentleman 

 employs them in the carrying out of a photo- 

 graphic process. An ordinary glass negative, 

 possessing an image which has been formed 

 by the deposition of silver particles, is pre- 

 pared in a suitable manner to protect it from 

 injury by contact with the mercury (such, for 

 instance, as coating it in some way with plati- 

 num or carbon particles), and the picture is 

 then exposed to the action of mercury-vapor. 

 The vapor condenses, in a more or less con- 

 centrated form, upon the image in the same 

 way, quite well, as it becomes deposited upon, 

 and develops the latent image in the daguerreo- 

 type process and subsequently the plate thus 

 treated is brought into contact with the sensi- 

 tive paper. The consequence is, that the 

 minute particles of mercury deposited all over 

 the image exercise a reducing action upon the 

 salts on the surface of the paper, and a print 

 of the original photograph results, possessing 

 the same gradation of tint as the original. 

 Indeed, when nitrate of silver is employed for 

 sensitizing the paper, the photograph secured 

 is in every respect similar to that produced by 

 light in the ordinary silver printing process, 

 and the picture is forthwith toned and fixed 

 in the same way, in fact, as one of these ; in 

 the one case, however, the reduction of the 

 silver salts has been brought about by mercury- 

 vapor, while in the other light alone has been 

 the reducing agent. Impressions obtained by 

 means of platinum and palladium salts need 

 simply to be washed in water in order that 

 they may be permanently fixed. These latter, 

 in truth, are so indestructible and inalterable 

 that they cannot be destroyed except by a 

 chemical agent which would at the same time 

 radically injure the paper or other basis upon 

 which they rest. 



This process of photography is not yet in 

 such an advanced state as to be of any practi- 

 cal importance; but, nevertheless, it is cer- 

 tainly one of the most ingenious and interest- 

 ing discoveries made of late in this branch of 

 science. The great advantage it possesses is 

 that of printing without the aid of light, and 

 yet producing prints with detail and half tone 

 dependent upon delicate chemical reaction 

 such rare gradation being secured as our pres- 

 ent light-printed pictures (silver and carbon 

 prints) alone possess. 



