Analyses of Books. 
[February, 
no 
abundance of pay-quartz. This practical skill is almost unerring 
within narrow limits. Under new conditions it breaks down. 
We could wish that these considerations had come undei th 
notice of Mr. S. Butler before he wrote a passage to prove the 
inferiority of the mining engineer to such prospectors But . M . . 
Williams continues : — “ Some of the most absurdly foolish fa o 
mining enterprises I have ever known have been set on foot by 
old Californian miners, who, returning to their foimer homes 
east of the mountains, have said at once of some ravine 01 hill- 
side that it was just the place for gold.” 
Every close observer will admit, as does the author, that there 
are many tokens by which the presence of water underground 
may be inferred. And the hydroscopist is really guided by these 
signs, and merely fancies that he is obeying the indications of 
^Thefbulk of the work before us consists, however, of a most 
elaborate account of the metallic ores and other valuable mine- 
rals known to exist in the United States. Under “ Vanadium 
we find the following strange passage Vanadic salts are 
extremely valuable, and are used principally as a mordant in the 
manufacture of the finest silks.” The chief use of vanadium 
compounds is in the development of aniline black upon cottons. 
‘I he Dynamo: liow made and how used. A Book for Amateurs. 
By S. R. Bottone. London : W • Swan Sonnenschein 
and Co. 
The purport of this book is explained in the title, brief as it is. 
The author, addressing himself to amateurs, gives exceeding y 
plain, clear instructions for the manufacture of small dynamos. 
He has in view the construction of such machines only as can 
be worked without power, and may “ replace a battery of eight 01 
ten cells without the disagreeable concomitants of changing 
acids and cleaning plates.” . , , , , • 
Here, of course, there is room for variety of tastes and apti- 
tudes. There are many persons who would find the care and 
management of a battery far less disagreeable and difficult than 
the construction of a dynamo, even by the aid of Signor Bottone s 
able instructions. But for those who have mechanical taste and 
skill the dynamo will doubtless be pieferable. 
The illustrations of this work are numerous, well executed, 
and intelligible. 
