Fig. 35. 
On a Series of Lantern Slides. By Dr. A. Clifford Mercer. 311 
bright surface it should cover has been quite commonly neglected and 
has been the cause of many poor results in photomicrography. 
In slide 52 (fig. 36) is seen a block of heavy wood which slides 
iu a direction parallel with the axis of the Microscope, without lateral 
