Al'Gl'ST. 1911. 



KNOWLEDGE. 



293 



iars or fibrils of silex, arranged 



formed of short 

 lengthways on the valve. The\' run in pairs, parallel 

 each pair having larger and narrower interspaces 

 between them in regular succession, and so placed 

 that the larger interspaces are set obliquel}- to the 

 corresponding interspaces between the other pairs, 

 both above and below. Figure 10, from another 

 valve, exhibits the same structure torn, and still more 

 plainly because the " chains " are more isolated. 

 Now, in explanation of the figures, his theorv is 

 this, that what we see in the P!ciii osi^iihi valve, when 

 sound, is not the structure at all. but simpK' a 



same valve mounted in a medium. The valve shown 

 in Figure 11 has been ruptured, leaving in some parts 

 the outer layer well separated from the under, in 

 others normal, ^^'e see, then, at the lower part of 

 the picture the characteristic structure ; in the middle 

 it is no longer visible, while at the top it re-appears, 

 though not so well indicated. Figures 12 and 13 

 are taken bv the oil immersion from the same spot, 

 the first with the glass slightly stopped down, the 

 second with the widest available aperture ; leaving 

 the image hv itself, in the air as it were. 



Now for all practical purposes Figure 12 is the 



Figure 11. The outer torn ^.tuutiue 



of another valve taken with the same 



lens as Figures 6 and S."' 



Figure 12. The -..um >[h . uu. n .i^ 

 seen in Figure 11, taUen with a two 

 millimetres objective of Zeiss, slightly 

 stopped down. < 1750. 



Figure 13. The same specimen as 



seen in Figures 11 and 12, taken with 



the fullest aperture available. 



collection of focal images thrown from the other 

 layer upon the one nearest the eye, just as a picture 

 is throv\n from the optical lantern upon a canvas 

 screen. The fibrils or grating is the real structure, 

 of which the texture is concealed, even as that of the 

 canvas screen is by the picture. We shall see more 

 of this further on. 



The next three figures, taken from the outside of 

 another valve, are given more to illustrate the value 

 of aperture than to elucidate structure. Figure 11. 

 photographed by the same drv lens as Nos. 6 and 8. 

 shows that it was not from want of aperture it failed 

 to exhibit the right structure. To repeat, it is 

 simply a matter of possessing too deep a focus to 

 separate the component la\ers. though a most superb 

 glass. No dry lens could do it when at the normal 

 distance apart, nor e\-en an oil immersion, with the 



most effective picture, as affording opportunitx' for 

 comparing the relationship of the two layers ; vet 

 it is always well not to give the enem\- cause to 

 blaspheme. When these researches began, the 

 results were put down b\- some to moisture in 

 the dry mount, to oblique light, to interference 

 phenomena ; to everv cause, in fact, except to 

 a revelation of new structure. Speaking gener- 

 allv. [lerhaps the most irritating of all criticisms 

 are those which, if the\' are valid, will not only 

 deprive one of all claims to be looked upon as 

 an accurate observer, but also of common sense in 

 conducting his researches. Naturalh-, in very self- 

 defence, one was put upon his metal, and. b\' 

 widening the aperture to the fullest a\'ailable, 

 produced photographs of which this last print and 

 others are examples. 



( To be cent i lilted., t 



Here the outer structure is only seen where it has been left against 



the under layer. 



cover glass more than the normal distance from 



