146 Anaiyses of Books. [Feb. 



the latter variety may be easily traced from the rhombic plate 

 by the incomplete developement of the smaller angles of the 

 usual rhomb." 



With respect to the elementary constitution of this substance. 

 Dr. Kidd says, that he is " not enabled to give any satisfactory 

 information ; but it is evident that it contains a very great pro- 

 portion of carbon." 



It is greatly to be regreted, that Dr. Kidd did not complete 

 his labours by giving an analysis of this curious substance. 



XVII. On the Ahevrations of Compound Lenses and Object 

 Glasses. By J. F. W. Herschel, Esq. FRS. &c. 



In the commencement of this elaborate communication, its 

 author remarks, that it has been made a subject of reproach to 

 mathematicians who have occupied themselves with the theory 

 of the refracting telescope, that the practical benefit derived from 

 their speculations has by no means been commensurate to 

 the expenditure of analytical skill they have called for. Mr. 

 Herschel has, therefore, in this valuable paper supplied the artist 

 with practical matter which cannot fail to prove of the highest 

 utility. 



XvIII. An Account of the Skeletons of the Dugongy tioo 

 horned Rhinoceros, and Tapir of Sumatra j sent to England by 

 Sir Thomas Stamford Raffles, Governor of Bencoolen. By Sip 

 Everard Home, Bart. VPRS. 



With respect to the dugong. Sir Everard remarks, that *' The 

 bones of the skeleton, when mounted, give us a form very differ- 

 ent from what is met with in the whale tribe. It may be com- 

 pared to a boat without a keel, with the bottom uppermost; so 

 that in the sea, the middle part of the back is the highest point 

 in the water ; and as the lungs are extended to great length on 

 the two sides, close to the spine, they furnish the means of the 

 animal becoming buoyant, and when no muscular exertion is 

 made, the body will naturally float in an horizontal posture. 



" When we consider that this animal is the only one yet 

 known" that grazes at the bottom of the sea (if the expression 

 may be allowed), and is not supported on four legs, we must 

 admit that it will require a particular mode of balancing its body 

 over the weeds upon which it feeds. 



" The hippopotamus, an animal that uses the same kind of food, 

 from the strength of its limbs, supports itself under water ; and 

 the dugong, as a compensation for not being able to support its 

 body on the ground, has this means of steadily suspending itself 

 in the sea peculiar to itself, the centre of the back forming the 

 point of suspension, similar to the fulcrum of a pair of scales. 

 This peculiarity of position explains the form of the jaws, which 

 are bent down at an angle with the skull, unlike the jaws of 

 other animals. This new mode of floating, when compared with 

 that of other sea animals, makes a beautiful variety. The balaena 

 mysticetus, that goes to the bottom of unfathomable depths to 



