114 [Assembly 



By comparison, Dr. Young's eriometer (wool-metre), for mea- 

 suring fibres and atoms, determined that a seed of tlie Lycopodium 

 (the club moss) was in diameter the 10,500 part of one inch. 



Milk, atoms of, 9,000 do 



Human blood , atoms of^ 4,000 do 



Silk fibres, do 2,000 do 



Cotton, do 1,400 do 



Saxony wool, do 600 do 



South Down wool, do 281 do 



Coarse wool, do 150 do 



The waves of red being about ^V millionth of an inch in length, 

 then as 100 grains of sand in diameter equal one inch, the length 

 of a side of one cubic grain contains about two millions of waves, 

 the side of the grain must contain four million millions, and the 

 whole cubic grain must contain eight million billions of these 

 waves. 



As the atoms of milk are goVo^l^ of an inch, then a cubic grain 

 of sand (which is accepted at j^gih of an inch) contains g^uth 

 part of x^'gth of one inch in length, and in cubic contents 7,290 

 millions ; the atoms of human blood in the size of the cubic grain 

 of sand, about 3,000 millions ; Lycopodium (club moss seeds), 

 more than 8,000 millions. 



A soap bubble, when about bursting, is | millionth of an inch 

 thick; or it would require half a million of then; to make a film 

 ^tli of an inch thick. 



Atoms less than ^ millionth of an inch are black, because they 

 are too small to reflect light. 



Frauenhofer actually made a machine with which he drew 

 S2,900 lines in the space of one inch. 



