OR, A TREATISE ON PILE. 102 
where it is about eight inches. To the latter, as a general rule, it may be observed that 
the smallest square magnitude visible to the naked eye, either of white particles upon a 
black ground, or of black particles upon a white ground, is ;}; of an inch, but when the 
substance is in “ines instead of particles, it may be seen, if held towards the light, when 
only z,457 of an inch in diameter. ‘The finest wool that we have examined, coming from 
the body of a sheep, is 545g part of an inch, which, according to the above rule, can be 
seen with the naked eye. There is a point beyond which an object cannot be seen; 
owing, perhaps, to the light being absorbed before it reaches the retina. This point, (which 
is called the “ vanishing point,’’) must, of course, depend upon the eye, the light, the color 
and the size of the object; where the light, the color and the size of two or more objects, are 
alike the distance of the vanishing point, to the same eye, must always be identical. Now we 
propose that a series of tubes, to draw out one from another, like those of a telescope, be con- 
structed of sufficient length that, when fully drawn, they are equal to the vanishing point of 
the coarsest wool desired to be examined. Upon apiece of card arrange a series of strands of 
wool, in the order of fineness, the diameters of which have been previously ascertained with 
the microscope and micrometer. Upon a similar card stretch a strand of the wool, the relative 
diameter of which it is required to ascertain, and, upon fixing it near one end of the tube, 
(one eye to the other end,) draw out till you find the vanishing point of the strand. Re- 
move this card and put the other one in its place, when it will be perceived which of the 
filaments upon it is at its vanishing poit, and the diameter of that strand will be the one 
required. ‘The tubes may be made of tin or even of pasteboard, but ought to be blackened 
inside. ‘The measured wool upon the cards can be procured in this city for a trifle. 
Or Hyperrropnuy on Unnatrurat Growru or Harr.—When hair grows to such an 
unnatural length as to cause disease, it is called “hypertrophy.”* Dr. Gross tells of a 
young lady who died of this disease She had always experienced an unusual growth of 
hair, and generally kept it cut short; but, a few months before her death, it grew down to 
her heels. It was flaxen and had a soft oily feeling. ‘The account concludes with the 
remark that a post-mortem examination showed that the unnatural growth of hair had 
caused her death.t 
Or Depitation.—Some Malays destroy the hair with quick-lime, the isolated ones 
being plucked out with tweezers. (Latham, Nat. Hist. of Var. of Men, 148.) Most 
American Indian tribes pluck out their beards. 
Or THE Discorome.—Deseription of a very convenient instrument for cutting transverse 
sections or disks of hair, which we call a Discotome. + 
h 
* From hyper uper, or above, and ¢rix, hair. 
} The corrosive medicines used to take away superfluous hair are called “ Ectillotice,” from “ck,” out, and ‘‘tillo,” to 
pluck. 
{ From discos, a disk, and femno, to cut. 
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