102 The Microscope. 



in a space of three-eighths of an inch square* 

 (No. 9). 



These photographs are taken with a photographic 

 camera, in which, instead of the large lens which has 

 stared at most of us in these days of cartes-de-visite, 

 one of the object-glasses of a microscope is used. 

 The pictures are taken on very carefully- 

 prepared iodized collodion, and developed 

 by pyrogallic acid or sulphate of iron. 



No. 9. When dry, they are mounted in Canada 

 balsam to protect them. 



Microscopic photographs were also the independent 

 invention of Mr. Shadbolt, in the year 1854. He 

 exhibited a number of them in that year, ranging 

 from the one-twentieth to the one-fortieth of an inch 

 each way, one of which was a pretty extensive view of 

 Paris. 



There is another class of objects which may be 

 described along with the microscopic photographs, 

 although the method of their production is quite dif- 

 ferent. These are some exquisitely minute specimens 

 of ruled lines and of writing done upon the glass with 

 a diamond point. 



Many microscopes are furnished with what is 

 called an eye-piece micrometer, used, as the name 

 imports, for measuring minute spaces. It consists of 

 a series of delicate lines, ruled by ingenious machinery 

 on glass at regular intervals, and crossed with others. 

 So many as ten thousand lines have been ruled in this 

 way in the diameter of an inch. The test-objects 



* " Photographic Journal," for April 15th, 1859. 



