264 NATURE'S TEACHINGS. 



the ridges, and to which is owing the unmistakable " bite " of 

 a real English file. 



But there are occasions when the hand of the most cunning 

 file-maker is baffled, and when it is necessary to cut files so 

 delicate that the unaided human eye cannot trace their teeth. 

 Art, therefore, has recourse to Nature, and the cabinet-maker, 

 who cannot obtain any file made by human hands which will 

 answer his purpose in the higher branches of his trade, makes 

 great use of the " Dutch Rush," as he calls it. It is not a rush 

 at all, but simply a species of Mare's Tail, or Equisetum, a 

 plant which fills in profusion almost every marshy spot in 

 England. 



The peculiar fitness of the Equisetum for this purpose 

 cannot be appreciated even by those who use it until it has 



EQDISETUM. 



been viewed under the microscope. I have now before me a 

 small piece of Equisetum, placed under a half- inch power, and 

 viewed by direct illumination, it being treated as an opaque 

 object. 



The microscope reveals at a glance the source of the power 

 which the ingenuity of man has taken advantage of. The 

 surface of the Equisetum is seen to be composed of myriads of 

 tiny parallel ridges, each ridge bristling with rows of flinty 

 spicules, looking very much like the broken glass upon the top 

 of a wall. Minute as they are, these spicules can do their 

 work, and they enable the joiner to finish off work in a manner 

 that could not be accomplished by any tool made by human 

 hands. 



I find, by recent inquiries, that modern joiners scarcely, if 

 ever, use the Equisetum, preferring emery-paper as cheaper 

 and more expeditious, and knowing that the popular eye is not 

 able to appreciate the difference of the surface obtained by 



