scope were to be cultivated by the majority solely 

 as a diversion, not only would it afford relaxation 

 and pleasure, but it would also develop among 

 keen amateurs another Fabre, perhaps, or a Hux- 

 ley, or an Agassiz. 



Let us now take our last look at P. angulatum. 



We have seen how this diatom, at a magnifica- 

 tion of five hundred diameters, under a dry lens, 

 appeared as having a striated, or screen-like, sculp- 

 turing. Observe then, that the immersion lens, to- 

 gether with the proper eyepiece, presents not only 

 a more highly magnified, but also a quite different 

 picture of this pattern. As we now see it, magni- 

 fied more than twelve hundred times, the lines, as 

 such, have disappeared and instead there is re- 

 solved a succession of dots: the striae in reality 

 consist of a series of small circular cavities, or 

 depressions, in the silicious shell. Arranged in 

 orderly rows, the exquisite appearance of such 

 minute and geometrically precise pips amazes the 

 beholder. Consider. The entire diatom is so small 

 as to be totally invisible to the ordinary eye. Still 

 it is completely covered with sculpturings of 

 round recesses so vastly smaller that when meas- 

 ured with a micrometer the diameter of these mark- 



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