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flDicro0copicaI technique. 



Compiled by W.H.B. 



Hodgrson's Compressor.-This simple form of parallel compres- 

 sor has been devised by Mr. J. V. Hodgson, of Birmingham, to 

 meet the requirements of those who wish for an effective instru- 

 ment at a moderate cost, and at the same time permitting the use 

 of dark ground and oblique illumination of wide angle. It con- 

 sists of a plate of brass, 3 in. by i3/^ in., with a central hole ^ in. 





in diameter, over which is cemented a cover-glass. On either side 

 of the hole IS an upright peg. The upper plate is diamond shaped 

 and the central hole corresponds to that in the lower plate The 

 two ends of the diamond carry stout tubes fitting closely to the 

 upright pegs of the lower plate, and enable it to be adjusted to a 

 nicety^ The upper plate cannot be raised by one hand alone. 

 Mr. Hodgson also makes a form in which the cover-glass on the 

 lower plate is sunk below the level, while the upper plate is 



