NATURAL PHILOSOPHY. 145 



in order to engrave the design afterwards: Prepare the block as 

 usual by coating it with some white substance, ground with gum and 

 water; also take a negative proof of the photograph in question, and 

 get a positive impression from it on paper prepared with charcoal, 

 according to M. Poncy's process. This impression, previously moist- 

 ened with an alcoholic solution of caustic potash of moderate strength, 

 is now laid, face downwards, on the block, and pressed upon the white 

 surface by friction with an ivory knife or burnisher. On removing 

 the paper, the design will be found clearly impressed on the block. 



Photography applied to Anatomy. An important scientific work is 

 in course of issue in Munich a Photographic Atlas of the Nervous 

 System of the Human Frame. The photographs are taken by Herr 

 Albert, the court photographer, and are done with clearness and 

 precision. There is an explanation published with the plates, in Ger- 

 man and French, by a professor of anatomy ; and the work is to be 

 completed in ten parts, each part containing five plates, and costing 

 about eleven shillings and sixpence. The first part is published, con- 

 taining the nerves of the head, which stand out as plain and fine as a 

 spider's web, in the. photograph. The importance of such a work for 

 students of anatomy can hardly be exaggerated. 



Ingenious Application of Photography. On the Chicago and Mil- 

 waukie Railroad a very beautiful application of the photographic art 

 is used on the "season passes" and "commutation tickets" to prevent 

 their illegal transfer. When a person applies for a season pass or 

 ticket, he incloses his photograph, taken on a small gummed label, and 

 this is pasted on the card which he receives. The conductor of the 

 train can thus see at a glance whether the bearer of a pass or ticket 

 carries the evidence of "the right man being in the right place." 



Photographs of Defaced Writing. M. Silvy, of Paris, has recently 

 reproduced photographically one of the curious old manuscripts of 

 early literature. He states that not only is the copy more legible 

 than the original, but certain passages which could not be deciphered 

 on the old parchment have been actually revived ; and this is particu- 

 larly visible on the last page, where a note, written in German under 

 the signature, has become both visible and legible, while there is not 

 a trace of it left on the original. This curious circumstance is ex- 

 plained as follows : " During the photographic process, the brilliant 

 and polished parts of the parchment reflect light much better than 

 those where the ink has been deposited. However colorless it may 

 appear, the ink has not lost its anti-photogenic qualities, opposed to 

 the photogenic ones of the parchment; and, thanks to this opposition, 

 black characters may be obtained on the sensitive surface, in return 

 for much paler ones on the original." 



Microscopic Photography. Professor Gerlach, of the University 

 of Erlangen, has obtained some photographs of microscopic objects 

 by a new method, which consists in taking the object itself as the 

 negative image, and then taking a magnified positive of this image, 

 and repeating the operation, alternately positive and negative, until 

 an image is obtained of such a size as to present details of structure 

 far exceeding in magnitude those obtainable by the most powerful 

 microscopes at present in use. 



The Sun's Autobiography. Mr. Godard, an English photographer, 

 13 ' 



