What did our Forefathers see in a Microscope? 439 



pre-achromatic Microscopes have left behind them, and which may 

 be put to the proof by similar work done in the achromatic times. 

 I allude to the measurement of the red corpuscle in human blood. 



Dr. Jurin made it yw^o ^ n - > Leeuwenhoek confirmed this 

 measurement ; Dr. Wollaston g^ in. ; MM. Prevost and Dumas 

 -j J 7 g in. ; Captain Kater 4^^ in. 



The measurement by the achromat is 3^90 ^ n - Dr. Jurin's 

 measurement is 75 p.c. too large ; Dr. Wollaston's 32 ; M. Prevost's 

 17 ; and Captain Kater's 15 p.c. too small. 



