Fig. 36. FRAUENHOFFER'S MICROSCCM-IS. 



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 Baillifs micrometer. 60. Jackson's micrometer. 61. 

 Measurement by the camera lucida. 62. Goniometers. MAGNI- 

 FYING POAVER : G3. 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 49 



No. 112. 



