348 



Divisibility of Matter. 



Many years ago, a curious calculation was made by Dr 

 Thomson, to shew to what degree matter could be divided, 

 and still be sensible to the eye. He dissolved a grain of 

 nitrate of lead in 500,000 grains of water, and passed through 

 the solution a current of sulphuretted hydrogen, when the 

 whole liquid became sensibly discoloured. Now a grain of 

 water may be regarded as being about equal to a drop of that 

 liquid, and a drop may be easily spread out so as to cover a 

 square inch of surface. But under an ordinary microscope, 

 the millionth of a square inch may be distinguished by the eye. 

 The water, therefore, could be divided into 500,000,000,000 

 parts. But the lead in a grain of nitrate of lead weighs 062 

 grain ; an atom of lead accordingly cannot weigh more than 

 3io7ooo;oopobth of a grain, while the atom of sulphur, which 

 in combination with the lead rendered it visible, could not 

 weigh more than 2,015,000,000,000 ? that is the two billionth part of 

 a grain. 



But what is a billion, or rather, what conception can we 

 form of such a quantity l We may say that a billion is a 

 million of millions, and can easily represent it thus : — 

 1,000,000,000,000. But a schoolboy's calculation will shew 

 how entirely the mind is Incapable of conceiving such num- 

 bers. If a person were able to count at the rate of 200 in 

 a minute, and to work without intermission twelve hours in 

 the day, he would take to count a billion 6,944,444 days, or 

 19,025 years 319 days. But this may be nothing to the divi- 

 sion of matter. There are living creatures so minute, that 

 a hundred millions of them might be comprehended in the 

 space of a cubic inch. But these creatures, until they are 

 lost to the sense of sight, aided by the most powerful in- 

 struments, are seen to possess organs fitted for collecting 

 their food, and even capturing their prey. They are, there- 

 fore, supplied with organs, and these organs consist of tis- 

 sues nourished by circulating fluids, which circulating fluids 

 must consist of parts or atoms, if we please so to term them. 

 In reckoning the size of such atoms, we must speak not of 



