Miscellanies. 211 



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 3Iechanics to Practical purposes ; 

 by Prof. James Renwick, 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. Two 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. 



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 leaving 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 yoij 

 to publish the explanation here given. — J. L. R^ 



