LEROY C. COOLEY. 119 



Fifth, Errors in reading very minute changes by 

 scale, which forbids the measurement of volumes with 

 entire exactness and, which, when reduced to their 

 lowest limits, become more serious as the volumes be- 

 come smaller, since the same error which may be neg- 

 lected when the volume is very large in comparison 

 will be a hundred fold more serious when the volume is 

 reduced to the hundredth part. Regnault's tubes were 

 gauged with great precision, and by the use of a cathe- 

 tometer he could read a difference of half a millimeter 

 with considerable exactness, and to forbid the multipli- 

 cation of the value of the error by small volumes he forced 

 a fresh supply of gas into his apparatus before every ob- 

 servation, until he should have the same large volume to 

 measure at the highest as at the lowest pressures. 



Nothing can better illustrate the progress of experi- 

 mental science during the two centuries than a compar- 

 ison of this powerful and refined apparatus of Regnault, 

 with the primitive bent tube employed by Boyle and 

 Marriotte. The latter contemplated the action of pres- 

 sure alone, as if it were an isolated principle in nature, 

 unhindered and unaided by any other, while the 

 former recognizes it as only one of many, each of which 

 asserts itself in determining the result. Seen from the 

 standpoint of Boyle's tube, natural phenomena are sepa- 

 rate effects of single causes ; there is a subject and a 

 predicate, but no modifiers. Boyle's tube bears a rela- 

 tion to Regnault's apparatus similar to that which the 

 simplest sentence framed by the schoolboy bears to the 

 smooth period of the rhetorician or the well-rounded ar- 

 gument of the skilled logician. 



The results of Regnault's experimental logic were at 

 once adopted into science. They may be summarized as 

 follows : 



First, That for neither of the gases operated on, viz., 



71 



