444 PROCEEDINGS OF THE AMERICAN ACADEMY. 



the present method adopted by which the equilibrium pressure and 

 change of volume were measured simultaneously, but even with this 

 new method the curve was followed down, from high temperatures and 

 pressures to lower temperatures and pressures. The domain of tem- 

 peratures and pressures in which Tammann worked (up to 3500 kgm.) 

 was approached with the distinct prejudice, therefore, that Tammann's 

 work was incorrect, because there seemed no possible connection be- 

 tween the curves given by Tammann and the curves at the higher 

 pressures. This prejudice makes more valuable, therefore, the essen- 

 tial verification of Tammann's work found at the low pressures. The 

 expected discrepancy was avoided by the remarkable versatility of ice 

 in appearing in diiferent forms. 



The experimental methods are in large part the same as those used 

 in the preceding paper on mercury. Reference is made to that paper 

 for detailed discussion. Where new methods have been necessary, 

 discussion is given here in the appropriate place. 



In presenting the data, the aim has been to give enough so that any 

 one could, if he wished, check the computations for himself Every one 

 of the original observations, except those marred by obvious accidents, 

 has been given. The table of contents should, however, enable one to 

 omit the generally uninteresting discussion of details of methods and 

 critical examination of data, and proceed to the discussion of the gen- 

 eral results. In connection with the equilibrium of the different solid 

 forms, it is suggested that some may find it clearer to read first the short 

 history of the experiment, the description of the general nature of the 

 experimental methods, and the description of the manner of appearance 

 of the new forms of ice given first under the heading " The curve 

 VI-L," and then under " The curve V-L." 



Contents. 



Introduction 441 



Characteristic Surface of the Liquid 446 



The Methods, Particularly that Used below 0° 447 



The Data 451 



Compressibility at 0° 451 



Compressibility at 22° 453 



Dilatation below 0° 458 



Equilibrium between the Various Solids and the Liquid 462 



Discussion of Tammann's Work 463 



The Method of the Present Investigation 463 



The Numerous Checks on the Accuracy of the Data 465 



The I-L Curve 467 



The Data, p, t, Av, AH, AE 468 



The Initial Compressibility of Ice I 472 



