1898] MICROSCOPICAL JOURNAL. 



Gates' Double Microscope. 



Apparently Professor Elmer Grates of Washington has 

 made one of the most important discoveries ever achiev- 

 ed by science — that a second microscope can be used to 

 view and magnify again a small part of the image pro- 

 duced by a first microscope. Thus the power of the 

 human eye is increased 3,000,000 times instead of 10,000 

 times, as hitherto, for though the humen eye cannot, of 

 course, see the image directly it can see a reproduction of 

 the image and thus microscopy is carried as far beyond 

 the present art as it is itself beyond the power of the eye. 

 His process is as follows : 



"On the Abbe plate, consisting of fine lines ruled close 

 together, a J-inch objective showed four lines and three 

 spaces. With a 1-6-inch it showed nine lines and eight 

 spaces. Then, taking a second, with a 2-3-inch objective, 

 or a 14 mm objective, it was focused upon the real image 

 of the microscope by introducing the ocular of the first 

 microscope, so that the plane of the second objective was 

 in the plane of the real image, and then two lines and 

 one space covered the entire field of vision. 



This is only, however, the first step. When I replace 

 the 2-3 objective of the second microscope the magnifica- 

 tion is 400 more diameters, but the image cannot be seen 

 by the eye. It must be photographed. With a one-twelfth 

 objective on the first microscope and a three-inch on the 

 second I get a magnification of 3,000,000." 



He is delighted with this discovery because he wishes 

 to study the constitutional units of the cell as modified 

 by the mental activities of that cell. A great difficulty 

 arises in the focusing of the projected image of the sec- 

 ond instrument upon the sensitive plate because beyond 

 360,000 diameters the eye cannot see the image, A 

 series of empirical approximations are used to find the 

 focus. He hopes yet to be able to photograph ten times 



