Notes. 



291 



side of the pillar by means of a stout conical * pin, which passed 

 through both the pillar and the limb, and which was capable of being 

 tightened up by a screw. The flat tripod foot was known as the bird's- 

 claw. This excellent form of mount, which from its construction 

 leaves plenty of room on the right-hand side of the Microscope for the 

 manipulation of the substage and the mirror, was afterwards adopted 

 by Powell for his iron Microscope, which I described in the Journal 

 for 1899, p. 209, and from which figs. 81 and 82 are reproduced. 



Fig. 81. 



Fig. 82. 





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.1 1 



The next Microscope made by Messrs. Powell and Lealand is not, I 

 believe, figured or described anywhere ; neither can we now assign a 

 precise date for it3 introduction. I have asked Mr. Thomas Powell 

 about it, and he tells me that his own instrument is dated 1855, and 

 that, as it was only worked at in odd times, it took a long time to 

 make. It is not improbable therefore that this model was brought out 

 after the Exhibition of 1851. It will be unnecessary to illustrate this 



* This and similar important details of Microscope construction mentioned in 

 these papers are not mere copies from books, but have been learnt by the examination 

 of existing Microscopes. 



x 2 



