92 
Remarks on the "Universal Screw. 
By Richard Beck. 
(Read May 26ili, 1859.) 
On tlie 12th of November, 1857, a sub-committee of the 
Microscopical Society reported on the Best Eorm of Universal 
Attachment of the Object-glass to the Body of a Compound 
Microscope. 
Their recommendation has since then been adopted by 
several opticians, and will, there is little doubt, be ultimately 
used by all. The subject is, I believe, one of some impor- 
tance to members of this Society ; if it were not so, I should 
hardly have ventured the following remarks upon a subject so 
purely mechanical. 
Full particulars of "the universal screw,^' as it is now 
termed, have been given in the report I have already alluded 
to^ but (fig. 1) showing the screws of the object-glass and of 
Eig. 1. 
Diameter outside screw . -8 Length of thread . -125 
„ inside „ . -7626 „ plain part -15 
Screw 36 threads to the inch. 
the nosepiece will perhaps be more readily understood than a 
mere repetition of the dimensions in figures only. 
The standard sizes for these screws are two of Whitworth^s 
plug and ring gauges (fig. 2) ; and I may here mention, as 
an instance of the accuracy with which these tools can be 
tested, that Mr. "Whitworth has a means of detecting an 
amount of variation which, if magnified ten times, is then 
barely visible in our most powerful microscopes. 
