100 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



this country, the rapid improvements made in the achromatic object- 

 glass left the reflecting Microscopes out of the race, and they have long 

 since entirely disappeared. 



Fig. 6. 



Old Microscope by Andrew Pritchard. — The old Microscope here 

 figured (fig. 7) is signed Andrew Pritchard, 263 Strand, London, both 

 on the tripod and on the body-tube. Pritchard, it is known, sold Micro- 

 scopes made by Andrew Ross and Hugh Powell, who at that time 

 (1830-45) worked for the trade. The present stand shows by details of 

 its style and workmanship that it was probably made by Andrew Ross. 

 It is similar to the two Microscopes figured and described in this 

 Journal in 1902 (pp. 251-2) and 190G (pp. 596-7), and yet is different 

 in various particulars, showing it to be a somewhat earlier model of 

 Pritchard's " Solid Tripod-stand Achromatic Microscope and Engiscope," 

 as described by him in his Microscopic Illustrations of 1838 (p. 92). 



The earliest form of this Microscope must have been made for 

 Pritchard in or just Ijefore 1834, and is figured in the plate facing the 

 title-page of the first edition of his Natural History of Animalcules, 

 1834. No description of the instrument is given, and only in one 

 sentence (p. 23) he speaks of his Achromatic Engiscope " recently 

 constructed." The present model shows several modifications and im- 



