102 ARRANGEMENT OP APPARATUS. 



more enlightened than ourselves, perceive that most 

 people even if they had the opportunities of Mr. 

 Woodward, lack the ability to use them. 



Mr. Wenham, as early as 1855, gave instructions 

 in the Quarterly Journal of Microscopical Science, for 

 improving Microscopic Photography. The plan tlieti 

 adopted is not to be recommended. Mr. Highley we 

 believe subsequently obtained very good results, but 

 his method rendered necessary the use of a special 

 apparatus, distinct from the ordinary microscope. 



Captain Abney has given a few good hints, and it 

 is to be regretted he has not told us more. The 

 impression left, after ft perusal of his opinions, was 

 that he must have worked with inferior lenses. He 

 considers that higher powers than the quarter- inch 

 do not give as good results, on account of "the 



diffraction images of parts of the object this 



being dependent on the relative sizes of the object 

 and of the aperture of the objective." This is directly 

 contrary to our experience, as no objectives gave such 

 good results as the eighth and one twenty -fifth of 

 Messrs. Powell and Leland. This was no doubt 

 owing to the proper relation between the size of the 

 object and the aperture of the glass being strictly 

 observed ; the adjustment for cover glass being made 

 at the same time with extreme accuracy ; and prin- 

 cipally because the balance between the power and 

 aperture of the condenser, and that of the object, 

 was more easily equalised with these objectives than 

 with any others. 



Good results can never be obtained unless we are 



