1120 The American Naturalist. [December, 
To the gem dealer the book is invaluable, as it gives him at once 
all that he needs in his business ; to the lover of art it will afford many 
an hour of pleasure ; to the gem collector it gives numerous points of 
interest concerning the rare stones; and to the mineralogist it will 
prove a veritable mine of information, even in those subjects with 
which he thinks himself already conversant. Nor will the general 
reader, if well informed, be disappointed in his perusal of its pages, 
for he will find everywhere items of news that will add to his stock of 
useful knowledge, and suggestions that will help to develop his appre- 
ciation of the beautiful. 
The setting in which the ‘‘Gems and Precious Stones of North 
America” appears is well worthy of such lovely products of nature. 
The publishers have spared no efforts to enhance their beauty by an 
appropriate mounting. The plates and illustrations in the volume are 
excellent, the letter-press is marred by few errors, the paper is heavy, 
soft, and well tinted, and the binding is very tasty, We expect to 
hear of the books meeting a ready sale during the coming holiday 
season, for surely no more acceptable gift could be imagined 
than a handsome volume on a topic of such interest as the production 
of exquisite gems in prosaic North America.—W. 
General Notes. 

GEOLOGY AND PALEONTOLOGY. 
The Age and Origin of the Crystalline Rocks of Mis- 
souri.'—The Geological Survey of Missouri is indebted to Mr. 
Haworth for a valuable paper on the age and origin of the crystalline 
rocks of that state. Mr. Haworth’s study of these rocks began in the 
summer of 1886, and he has ever since pursued the subject with 
enthusiasm and zeal. His paper embodies the more important results 
obtained from a somewhat extended examination of the crystalline 
rocks in the vicinity of Pilot Knob. Field work has been supplemented 
with laboratory examination, and his conclusions are as follows: 
I. As to age, he agrees with other — in referring them to 
Archean time. 
1The Age and Origin of the reser Rocks of Missouri. By Erasmus Haworth. 
Bull. No. 6, Geol. Surv. of Misso 


