HISTORY OF THE MICROSCOPE. 5 



appeared distinct and prodigiously magnified when held 

 close to his eye, concluded, that if he placed a globule of 

 water in which there were any particles more opaque than 

 the water near his eye, he should see those particles dis- 

 tinctly and highly magnified. The result of this idea far 

 exceeded his expectation. His method was, to take on a 

 pin a small portion of water which he knew contained 

 some minute animalcules ; this he laid on the end of a 

 small piece of brass wire, till there was formed somewhat 

 more than a hemisphere of water ; on applying it then to 

 the eye, he found the animalcules enormously magnified ; 

 for those which were scarcely discernible with his glass 

 globules, with this appeared as large as ordinary-sized 

 peas. 



Dr. Hooke thus describes the method of usino^ this 

 water- microscope : " If you are desirous," he says, " of 

 obtaining a microscope with one single refraction, and 

 consequently capable of procuring the greatest clearness 

 and brightness any one kind of microscope is susceptible 

 of, spread a little of the fluid you intend to examine on 

 a glass plate ; bring this under one of your globules, then 

 move it gently upwards till the fluid touches the globule, 

 to which it will soon adhere, and that so firmly as to bear 

 being moved a little backwards or forwards. By looking 

 through the globule, you will then have a perfect view of 

 the animalcules in the drop." 



The construction of the single microscope is so simple, 

 that it is susceptible of but little improvement, and has 

 therefore undergone few alterations ; and these have been 

 chiefly confined to the mode of mounting it, or to addi- 

 tions to its apparatus. The greatest improvement this 

 instrument has received was made by Lieberkuhn,i about 

 the year 1740 : it consists in placing the small lens in the 

 centre of a highly-polished concave speculum of silver, by 

 which means a strong light is reflected upon the upper 

 surface of an object, which is thus examined with great 

 ease and pleasure. Before this contrivance, it was almost 

 impossible to examine small opaque objects with any 

 degree of exactness ; for the dark side of the object being 

 next the eye, and also overshadowed by the proximity ot 



(1) Dr. Nathaniel Lieberkuhn of Berlin. 



