MATTER AND ITS PHYSICAL PROPERTIES. 25 



bar is then wiredrawn, as in the first example, until it is reduced to a thread 

 so fine that thirty-four hundred feet of it weigh less than an ounce. The wire 

 is then flattened, by passing it between rollers under a severe pressure, a pro- 

 cess which increases its length, so that about four thousand feet shall weigh 

 one ounce. Hence one foot will weigh the four thousandth part of an ounce. 

 The proportion of the gold to the silver in the original bar was that of two to 

 three hundred and sixty, or one to one hundred and eighty. Since the same 

 proportion is preserved after the bar has been wiredrawn, it follows that the 

 quantity of gold which covers one foot of the fine wire is the one hundred and 

 eightieth part of the four thousandth of an ounce : that is the seven hundred 

 and twenty thousandth part of an ounce. 



The quantity of gold which covers one inch of the wire will be twelve times 

 less than that which covers one foot. Hence this quantity will be the eight 

 million six hundred and forty thousandth part of an inch. If this inch be again 

 divided into one hundred equal parts, every part will be distinctly visible with- 

 out the aid of microscopes. The gold which covers this small but visible por- 

 tion is the eight hundred and sixty-four millionth part of an ounce. 



But we may proceed even further. This portion of the wire may be viewed 

 by a microscope which magnifies five hundred times, so that the five hundredth 

 part of it will thus become visible. In this manner, therefore, an ounce of 

 gold may be divided into four hundred and thirty-two thousand million parts. 

 Each of these parts will possess all the characters and qualities which are 

 found in the largest masses of the metal. It retains its solidity, texture, and 

 color ; it resists the same agents, and enters into combination with the same 

 substances. If the gilt wire be dipped in nitric acid, the silver within the 

 coating will be dissolved, but the hollow tube of gold which surrounded it will 

 still cohere and remain suspended. 



The organized world offers still more remarkable examples of the inconceiv- 

 able subtilty of matter. 



The blood which flows in the veins of animals is not, as it seems to be, a uni- 

 formly red liquid. It consists of small red globules, floating in a transparent 

 fluid called serum. In different species these globules differ both in figure and 

 in magnitude. In man, and all animals which suckle their young, they are 

 perfectly round or spherical ; in birds and fishes, they are of an oblong sphe- 

 roidal form. In the human species, the diameter of the globules is about the 

 four thousandth part of an inch. Hence it follows that in a drop of blood which 

 would remain suspended from the point of a fine needle, there must be about a 

 million of globules. 



Small as these globules are, the animal kingdom presents beings whose whole 

 bodies are still more minute. Animalcules have been discovered, whose mag- 

 nitude is such, that a million of them do not exceed the bulk of a gram of sand, 

 and yet each of these creatures is composed of members as curiously organized 

 as those of the largest species ; they have life and spontaneous motion, and are 

 endued with sense and instinct. In the liquids in which they live, they are 

 observed to move with astonishing speed and activity ; nor are their motions 

 blind or fortuitous, but evidently governed by choice and direction to an end, 

 They use food and drink, from which they derive nutrition, and are thereto 

 furnished with a digestive apparatus. They have great muscular power, and 

 are furnished with limbs and members of strength and flexibility. They are 

 susceptible of the same appetites, and obnoxious to the same passions, the gra 

 fication of which is attended with the same results as in our own specie 

 Spallanzani observes that certain animalcules devour others so voraciously tJ 

 they fatten, and become indolent and sluggish, by over-feeding. 



After a meal of this kind, if they be confined in distilled water, so as t 



