378 No/ ices respecting Nexo Booh. 



with the natural histor}-, physiology and diseases of what he 

 properly terms " those primary instruments of the alimentary 

 process the teeth, his researches on which subjects lead him 

 to believe, 



" I. That enamel is constituted by a longitudinal arrange- 

 ment of prisms ; and that each prism is made up of an aggre- 

 gation of molecules, each distinct figure of which is a rhomb. 



" II. That longitudinal cracks of the enamel are directed 

 by the corresponding arrangement of its prisms; and that 

 they may be rendered undulating, as they often appear by the 

 rhomboidal figure of those molecules, which in the aggregate 

 compose the prism. 



" III. That the arrangement of the rhomboidal molecules 

 directs the diagonal fracture of the enamel. 



" TV. That the aggregation of rhomboidal molecules me- 

 chanically facilitates the disintegration of the enamel by com- 

 pression from the lateral surfaces of adjoming teeth, thereby 

 giving extraneous matters an opportunity of acting at large 

 upon the whole substance of the tooth compressed. 



" V. That the aggregation of the molecules is favourable 

 in particular to the insidious agency of acrid and decomposing 

 fluids, which are modified as to their chemical influence by the 

 state of the stomach, by various matters of aliment as soon as 

 they come within the lips, and by various nostrums which are 

 used for cleaning the teeth, and, according to the language of 

 quackerj', ' strengthening the gums.' " 



It will be seen, from the foregoing glance at a few of the 

 subjects of this volume, that it contains much, not only to en- 

 gage the attention of the philosophical as well as the medical 

 student, but to interest and instruct the general reader. 



A Celestial Atlas, comprising a Systematic Displa^j of the Hea- 

 vens, in a Series of Thirty Maps. Illustrated hij Scientifc De- 

 scriptions of their Contents : and accompanied hy Catalogues 

 of the Stars. With Astronomical Exercises. By Alexander 

 Jamieson, A.M. 



We congratulate the astronomical student, and the lovers 

 of one of the most delightful of sciences, on the valuable help 

 they will receive f> om Mr. Jamieson's Celestial Atlas, which is 

 not only calculated to facilitate the study of astronomy, but to 

 give a new charm to the contemplation of the starry heavens, 

 by pointing out how it can be rendered most agreeable and in- 

 structive. 



The idea of a Celestial Atlas was first suggested by our im- 

 mortal countryman Flamstead, whose great Atlas was the ba- 

 sis of M. de la Caille's Atlas Ccelestis ; for the latter merely 

 reduced the English astronomer's maps, and rectified the stars 



for 



