190 



EECEEATIVE SCIENCE. 



useful as they are interesting, is to find a way 

 of preventing the subsequent colouring of the 

 white parts upon exposure to daylight." 



Cattses of Wedgewood's and Davy's 

 FAiiitTBB. — After these results by Wedge- 

 wood and Davy, no experiments were made 

 for many years ; their failure owing solely to 

 the fact that the agents now used with such 

 success to fix the image by acting on the 

 nitrate of silver, were then unknown. Hypo- 

 sulphate of soda, discovered by Sir John 

 Herschel in 1819, and iodine, discovered in 

 1812, were then unknown, and without the 

 discovery of these or similar agents, photo- 

 graphy would probably never have reached 

 its present point of perfection. 



The DAGiTEEEEOTTrE. — So named after 

 Daguerre, who commenced his experiments 

 jn 1824, and having become acquainted with 

 Niepce in 1826, they pursued their experi- 

 ments together. In 1829, they employed 

 " iodine," from sea-weed, to blacken the plate 

 which held the heliographic impression, which 

 they applied with the greatest success to that 

 purpose. It took about twenty minutes to 

 obtain an impression. The picture is taken 

 on a copper-plate with a silver surface, now 

 under the operation of M. Claudet, who 

 adopts the Daguerreotype, and whose system 

 is said to be followed by all the so-called 

 American inventions. 



The Discoveeies oe Niepcb and 

 Dagueeee. — In 1814, Niepce, after a series 

 of experiments, succeeded in fixing the images 

 of the camera obscura, having discovered the 

 peculiar property of the solar rays to alter 

 the solubility of resinous substances. He 

 spread a thin layer of asphalte on a glass or 

 metal plate in the camera obscura, and, after 

 waiting from five to six hours, he found on 

 the plate a latent image, which became vi- 

 sible on treating the surface of the plate with 

 a solvent. In 1827, he made experiments at 

 Kew, and some of the pictures are said to be 

 preserved there. 



Invention op the Collodion Peo- 

 cess. — A friend of the late Mr. Scott Archer, 

 the inventor of the collodion process, says 

 that on September 19, 1850, Mr. Archer 

 communicated to him his discovery, and they 

 made the first coUodion picture together. He 

 had previously imparted the secret to one or 

 two friends, who assumed to themselves more 

 or less of the credit of the discovery. The 

 collodion process undoubtedly ranks above 

 all others, both as a sensitive medium, 

 and for the exactness and beauty of the 

 images it develops. It is so instantaneous 

 in its action that clouds, waves, ships, aud 

 figures in motion, may be taken by a siogle 

 lens. 



Chaeles Maybuey Abciiee. 



SPOETIYE EXEECISES UPON MUSICAL NOTATIOjS". 



IN TWO PAETS. — PAET I. 



The present paper is* intended to serve the 

 laudable purpose of impressing upon the 

 mind the names, relative value, and use of 

 the ordinary musical signs. It does not pre- 

 tend to contain aU, or even the half, of what 

 might be done in the same way ; but may 

 prove useful, as well as amusing, upon the 

 principle of verbum sapienti. Every one is 



presumed to have learned a little of musin ; 

 not every one can read a page of musii al 

 notes. The Sportive Exercises, by presenting, 

 in the form of problems, the simplest rules 

 and terms of musical notation, may afford, in 

 the hands of a teacher, armed with chalk and 

 black board, an hour's profitable recreation 

 to a class, and at the same time give the soli- 



