no DIATOMS 



be compared with these marvels of regularity 

 and exquisite beauty. 



To illustrate this chapter there are sis 

 pictures. The first is taken from a photo- 

 micrograph of 1,500 diameters. The diatom 

 is Actinocyclus ralfsii (Fig. 6). Under the 

 microscope this object gives a display of colour 

 very much resembling the action of a diffrac- 

 tion grating. 



The second is a magnificent diatom (Fig. 5). 

 In the original photo-micrograph it shows an 

 amplification of 2,500 diameters ! It was found 

 in clay in Hungary. 



The third is Navicula lyra (Fig. 30). The 

 illustration is from an amplification of 1,500 

 diameters ; the exposure was 60 minutes ; 

 the focal length 40 inches; an eye-piece 

 of 7 diameters; and the ^th objective were 

 used. 



Next comes the ' sun shield/ Heliopelta 

 metii (Fig. 3). The illustration is from a 

 photo-micrograph taken under a magnification 

 of 580 diameters. No collection of diatoms 

 can be representative without this specimen. 



