420 Dr. G. J. Stoney on the 



way of quantitatively estimating such events, we shall require 

 another and more acute-angled gauge to aid us in appre- 

 ciating them. 



VII. Of the Borderland of the Visible. 



Meanwhile the gauge now proposed will, it is hoped, help 

 the scientific student to obtain a more connected view of 

 nature, by placing before him in somewhat clear evidence the 

 relation in which some of the larger molecular events stand 

 to the dimensions of the smallest objects he can see with his 

 microscope. 



He should never forget that even the most minute of these 

 microscopic objects is an immense army of molecules*, or 

 semi-molecules, crowded together, more numerous indeed 

 than all the inhabitants of Europe. The individuals that 

 constitute the battalions are not seen, nor is there the least 

 glimpse of the active motions that are without intermission 

 going on among or within the individuals : nay more, waves 

 of light are too coarse to supply our microscopes with infor- 

 mation about the evolutions of the companies, regiments, and 

 brigades of this great army. It is only when the entire army 

 shifts its position that anything can be seen ; and my object 

 will be attained if the contrivance I have proposed helps in 

 any degree to bring about a better balance of thought rela- 

 tively to the cosmos in which we find ourselves : it is so 

 difficult to avoid making the small range of our senses a 

 universal scale with which to measure all nature. Where, 

 for instance, is the justification for our alleging that any 

 visible speck of protoplasm is undifferentiated ? And, in fact, 

 are not subsequent events perpetually rebuking this rashness ? 



A convenient object to help in connecting visible with 

 ultra-visible magnitudes, is the marking on the frustule of 

 the Pleurosigma angulatum (or, Gyrosigma angulatum), one 

 of the commonest of test-objects. The little brown specks are 

 easily seen with the higher powers of a microscope if a good 

 condenser and the proper stop be used, and their distance 

 asunder from centre to centre is somewhere between '64 and 

 •65 of a micron, according to the best determinations I can 

 make. This is a trifle more than the spacing deduced from 

 Professor Smith's measurement of the interval between the 



* That is, of molecules such as are present in the gaseous state of the 

 ultimate chemical constituents of the speck of matter under examination. 

 These in a highly organized substance like protoplasm are associated into 

 much larger organic groups, that may be called mega-molecules, and may 

 be likened to the companies or regiments of the brigades and corps that 

 make up the army. 



