Miscellanies. . OH 
6. On melanosis, animal pigments, and the philosophy of adventitious 
growth. . 
V. Comparative merits of the Hippocratic and Anatomical schools. 
VI. On the principal writings of P. Ch. A. Louis, M.D. With this 
essay the work closes. 
The typography of the work is very well executed, and does credit to 
the publishers; but it is inexcusable to publish any elaborate work without 
an index. 
35. Applications of the Science of Mechanics to Practical purposes ; 
by Prof. James Renwicx, LL. D., of Columbia College. New York, 
Harper & Brothers, 1840. 12mo. pp. 327. 
The distinguished author of this little volume states in the preface that 
in it he has endeavored to exhibit, in as popular, and at the same time as 
condensed a form as possible, the principles and leading facts of the 
application of the theory of mechanics to useful purposes.” A work of 
this description from Prof. Renwick is worthy the attention of every prac- 
tical man. 
36. Entomological Cabinet —Dr. C. G. Page wishes to dispose of his 
entomological cabinet, comprising about two thousand species and nearly 
a thousand duplicates. T'wo thirds are natives, and with the exception of 
about one hundred, were obtained from the vicinity of Boston, Massachu- 
setts. The remainder is a choice selection from Maranham, Java, Japan, 
and China. The cabinet is in excellent order, and the characteristic dis- 
tinctions of the Lepidoptera particularly are uncommonly well preserved, 
as most of them were raised from the eggs, in a cocoonery, purposely for 
the cabinet. (The specimens are mostly classified and named.) This 
collection is offered for four hundred dollars. Apply to Dr. Charles G. 
Page, Washington, D. C. 2 ; 
37. Hog Wallow Prairies.*—Extract of a letter to the Editors from 
Prof, J. L. Riddell, dated New Orleans, May 23, 1840.—While in Texas 
the second time I had full opportunity to study the phenomenon of “hog- 
wallow prairies.” The long droughts in summer cause the woodless sur- 
face of the prairies to crack deeply, and oftentimes symmetrically ; sub- 
sequent rains wash the adjacent earth into these cracks, filling them up, 
converting them into little valleys, and jeaving intermediate hillocks, 
Next year the same round of cause and effects occurs in the same places, 
and thus successive years contribute for a long time to produce a maxi- 
* As I make mention of this appearance in my notes on the Trinity country, 
published in your Journal last summer, without assigning a cause, I will ask you 
to publish the explanation here given.—J. L. R. 
& 
