MEASURING DRY MASSES WITH INTERFERENCE MICROSCOPES 225 



factor. Figure 8.18 shows, using the fringes method, the photograph 



of a drop of water deposited on a not thoroughly clean glass plate. 



The method is applicable to the study of small insects, such as 



"flying" arthropoda. Such insects float on the water because they are 



Fig. 8.18. Drop of water deposited on a not thoroughly clean glass plate. 



Fig. 8.19. Water surface deformation produced by a small insect (Velia). The deformations 



are observed using the fringes method. 



