268 PROGRESS OF SCIENCE. 



end, and therefore an instrument of varied powers, how 

 mathematics have stamped with the mark of truth countless 

 solutions in chemistry, physics, geology, mineralogy, astro- 

 nomy, we cannot for a moment doubt after reading the 

 preceding chapters of this work, much less after reading 

 the history of any of these branches. Even unpretentious 

 instruments have proved invaluable. It has been well 

 pointed out by Liebig that chemistry is deeply indebted 

 to four things which to all appearance are insignificant 

 agents, viz., glass, cork, India rubber, and gas ; the absence 

 of any one of these four things would have caused the 

 impossibility of undertaking a certain number of investiga- 

 tions, and their collective absence would have made chemistry 

 relatively barren in recent times ; whereas their united effects 

 have secured a harvest of products which have enriched the 

 whole of the working world. Thus does human intellect 

 derive powerful assistance from materials and appliances, 

 little in themselves perhaps, but fruitful of innumerable benefits. 

 Another standard of the value of instruments, besides their 

 material and profitable assistance, lies in the reliance we 

 can repose in their accuracy in the solution of problems 

 which demand minute exactness : we can now perceive 

 the 9 ; oooth part of a degree in temperature, i,coo,oooth 

 of a second in time, i ; ooo y oooth of an inch in space, 

 i ; ooo,cooth of a gramme in weight, the presence of the 

 io,ooo,oooth part of a gramme of a substance. We can in 

 fact observe "quantities 300,000 cr 400,000 times as small 

 as in the time of the Egyptians." Where would the eye 

 or the intellect be without instruments? We owe to them 

 our most surprising results. 



