OF ARTS AND SCIENCES. 353 



" On the other hand, the elaidic and gaeidinic acids are both un- 

 changeable in the air, as well as their ether compounds. And they 

 and their ether compounds can be distilled without undergoing de- 

 composition. These acids also possess higher melting-points respec- 

 tively than the oleic and hypogaeic acids, although we observe here 

 the remarkable distinction, that, while accompanying the transforma- 

 tion of oleic acid into elaidic acid there is an elevation of 31° C. in 

 the melting-point, the same transformation of hypogseic into gaeidinic 

 acid produces a change of but 4° C. in the melting-point. 



" The correspondence between the gaeidinic and elaidic acids is 

 also further established by the relation between their melting-points. 

 They differ by C4 H4 in constitution, and their melting-points differ by 

 about seven degrees. As Heintz has shown in regard to the other 

 series of fatty acids, a difference of from 7° - 10° C. in the melting- 

 points corresponds to a difference of C4 H4 in constitution ; this rule 

 holds good within certain limits so far as the melting-points have been 

 accurately determined. 



" These results, then, show that, under the influence of nitrous acid, 

 hypogaeic acid behaves in a manner precisely similar to that which 

 characterizes oleic acid under the same circumstances. 



" Farther, as the results of our investigation have proved, sebacic 

 acid is one of the products of the dry distillation of hypogaeic acid. 

 Thus, that correspondence between the characteristic properties of 

 these two acids which we should have a right to expect with two 

 bodies standing near to one another in the same series, does not 

 fail to hold good in every important respect. And this result is inter- 

 esting, as no other member of this series of acids which has yet been 

 'discovered has yielded such satisfactory results. 



"It is to be hoped, that further investigation on this series may de- 

 velop a more complete correspondence between its members ; for, 

 as they now stand, there is hardly sufficient resemblance in their 

 properties alone to suggest a classification of all of them together. 

 The principal reason for this classification being founded in their con- 

 stitution alone." 



Professor Agassiz said, that, in the course of his recent 

 studies of the Turtles, he had been anxious to ascertain whether 

 the different stages of embryonic development, and the differ- 

 ent orders of this class, corresponded with the different stages 



VOL. III. 45 



