Fig. 36 .—Frauenhoffer’s Microscope. 
THE MICROSCOPE. 
CHAPTER IV. 
Pritchard’s analysis of the effects of illumination (continued). Mea¬ 
surement of objects : 54. Measurement distinct from magnifying 
power.'—55. Measurement by comparison with a known object.— 
56. Micrometric scales.—57. Thin glass plates.—58. Micrometers. 
—59. Le Eaillif’s micrometer.—60. Jackson’s micrometer.—61. 
Measurement by the camera lucida.—62. Goniometers. Magni¬ 
fying Power : 63. This term much misunderstood.—64. Its exact 
meaning.—65. Least distance of distinct vision.—66. Visual esti¬ 
mate of angular magnitude.—67. Method of determining magnifying 
power by the camera lucida.—68. Dimensions of the least object 
which a given power can render visible. 
Lardner’s Museum of Science. e 
No. 112. 
45 
