The Microscope 



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Vol. VII. DETROIT, OCTOBER, 1887. No. 10 



ORIGINAL COMMUNICATIONS. 



1. MICEOSCOPICAL TUBE-LENGTH, ITS LENGTH IN 



MILLIMETERS, AND THE PARTS INCLUDED 



IN IT BY THE VARIOUS OPTICIANS 



OF THE WORLD. 



II. THE THICKNESS OF COVER-GLASS FOR WHICH 

 UNAD JUST ABLE OBJECTIVES ARE CORRECTED.* 



s. h. gage. 



TN the construction of microscopic objectives, the corrections must 

 -■■ be made for the formation of the image at a definite distance, 

 or, in other words, the tube of the stand of the microscope on which 

 the objective is to be used, must have a definite length. Conse- 

 quently, the microscopist must know and use this distance or 

 " microscopical tube-length'' to obtain the best results in using the 

 objective in practical work. 



In order to ascertain the exact distance in millimeters for which 

 objectives are corrected, and the parts of the microscope included 

 in this distance or '* tube- length," the following questions were 

 submitted to all the opticians of the world whose address could be 

 obtained: 1. For what "tube-length" do you correct your micro- 

 scopic objectives ? Please give the length in millimeters or inches. 



2. Please indicate on the diagram on the opposite page (fig. 1 of 

 this paper) exactly what parts of the microscope you include in 



* Transactions American Society of Microscopists, 1887. 



