8 PROCEEDINGS OP THE AMERICAN ACADEMY 



or about four per cent. A glance at the page referred to will show, 

 however, that of these ten measurements but six were at the tempera- 

 tures of 0° and 100 respectively. These six as shown in Table II. 

 give the mean 



_ lioo _ ;^ 270 ± a.d. 0.005, 



and this mean I shall use in comparing this series with the later ones, 

 omitting those results obtained at temperatures between 0° and 100°, 

 because the want of certainty in the temperature measurements would 

 render the labor of the necessary computations fruitless. 



TABLE I. 



TABLE II. 



Second Series. April, 1878. — In making a study of the best forms 

 of apparatus, a careful trial was given to capillaries in the form of a 

 helix, as these facilitate the maintenance of constant and uniform tem- 

 peratures of the bath, and render the use of longer and larger tubes pos- 

 sible. The coils were successfully made by winding the tubing, as it 

 was drawn from the tube of tlie glass-worker, upon a wooden drum. 

 The second series was made with a pair of such coils, and consisted of 

 only eight measurements. The results in the measurements of K were 

 so wholly discordant, that they were at once rejected. 



Third Series. — A second pair of smaller coils was mounted in a 

 manner similar to that just described, and with the same general 

 results, showing the coils to be utterly useless; probably, as was to 



mean, and 



(J, + d, + d,+ dn 



will be the average deviation, if, in the 



summation of the numerator, the values of d^, d^, &c. be taken arithmetically, 

 without regard to algebraic sign. 



