118 THE PRINCIPLES OF SCIENCE. 



sible to trace a line among the points which will approxi- 

 mate to the true law more nearly than the points them- 

 selves. The accompanying figure sufficiently explains 

 itself. 



VARIABLE 



Perkins employed this graphical method with much 

 care in exhibiting the results of his experiments on the 

 compression of water k . The numerical results were 

 marked upon a sheet of paper very exactly ruled at 

 intervals of one-tenth of an inch, and the original marks 

 were left in order that the reader might judge of the 

 correctness of the curve drawn, or choose another for 

 himself. Regnault carried the method to perfection by 

 laying off the points with a small screw dividing engine * ; 

 and he then formed a table of results by drawing a con- 

 tinuous curve, and measuring its height for equidistant 

 values of the variable. 



Not only does a curve drawn in this manner enable 

 us to assign by measurement numerical results more free 

 from accidental errors than any of the numbers obtained 

 directly from experiment, but the form of the curve 

 sometimes indicates the class of functions to which our 

 results belong 



k ' Philosophical Transactions,' 1826, p. 544. 

 * Jamin, ' Cours de Physique,' vol. ii. p. 24, c. 



