192 The American Geologist. March, 1894 
author is evidently not familiar with Prof. Kimball's account of the for- 
mation of the Cuban ores by the "isomorphous and pseudomorphous 
replacement of limestone," which is one of our most valuable memoirs 
on the subject. 
The idea that iron mines are all worked in open pits is so frequently 
expressed that it seems necessary to call attention to the fact that 
nearly all of the iron mines (150 or more) of the lake Superior region are 
underground and have attained depths varying from 400 to 1,600 feet. 
No particular mention is made of the Homestake gold mine in the 
Black Hills, although it is an important producer and well illustrates 
one classof gold mines, — those contained in a belt of crystalline schists. 
The occurrence of native silver in calcite veins in the Silver Islet and 
other mines of Thunder bay is also overlooked. 
On page 210 the depth of the Calumet and Hecla copper mine is in- 
correctly stated to exceed 4,000 feet; and on page 269 we are told that 
manganese is less valuable than iron and therefore not ordinarily mined 
unless collected into extensive beds, neither of which statements is 
strictly true. 
There is a valuable chapter on coal and another on petroleum and 
natural gas. On these products, as on building stones, clays, cements, 
and soils, the information is accurate and up to date. Rock salt is 
rather briefly mentioned, but here as throughout the book the author 
has availed himself of the most recent statistics as to production. 
The work is a welcome addition to our scanty literature on mineral 
products and is exceedingly creditable to its author. It is gratifying 
to learn that it has already been adopted in ten or more colleges as a 
text-book. For general students it is admirable, but for mining engi- 
neers something like Kemp's "Ore Deposits of the United States," more 
specilic in description and exact in reference, will be used. 
H. V. W. 
Geology of the Boston Basin. Vol. i,Part i. — Nantosket and Cohas- 
set. By William O. Crosby. (Occasional Papers of the Boston Society 
of Natural History. IV.) Pp. 177, with two maps, four plates, and 23 fig- 
ures in the text. 1893. This is the first of a series of memoirs to treat 
of the geology of the area reaching to distances of five to fifteen miles 
or more from Boston, Mass., upon which the author has devoted much 
observation and study from the time of his publication of a geological 
map of the district for the Philadelphia Centennial Exposition in 1876. 
The tract here described is the peninsula of Nantasket, enclosing Bos- 
ton harbor on the southeast, with the adjoining mainland township of 
Cohasset. The very ancient lava flows of the Boston basin and their 
relations to the interstratified conglomerate (Roxbury puddingstone) 
are here observed better than in any other localities. Professor Crosby 
shows that the melaphyrs and porphyrites were mainly contemporane- 
ous lavas poured out on the sea-floor at different times during the depo- 
sition of the beds of conglomerate and sandstone. The granite and 
diorite of the area are newer than the Cambrian slates of Braintree and 
Weymouth; it is also clear that the conglomerate and melaphyr sheets 
