Parkinson on Fossil Organic Reviaiiis. 139 



, In another note the author, speaking of his reasons for 

 avoiding the use of fluxions, expresses himself thus : 



" I have rejected fluxions in consequence of the very ob- 

 scure manner in which its principles have been explained by 

 the writers I have consulted on the subject. I cannot recon- 

 cile the idea of one of the terms of a proportion vanishing for 

 the purpose of obtaining a correct result ; it is not, it cannot 

 be good reasoning; though, from otlier principles, I am aware 

 that the conclusions obtained are correct. If the doctrine 

 of fluxions be fi-eed from the obscure terms, limiting ratios, 

 evanescent increments, and decrements, &c. it is, in reality, 

 not very difficult. If you represent the increase of a variable 

 quantity by a progression (as is done in art. 249. sect, vii.) 

 the first term of that progression is the same thing as what is 

 called a fluxion ; and the sum of the progression is the same 

 as a fluent. A fluxion is, therefore, the first increase of an 



increasing variable quantity ; and the last decrease of a de- 

 creasmg one, and the expansion of a variable quantity into a 

 progression, is the best and most clear comment that can be 

 added to the lemmas of Sir Isaac Newton." 



We cannot too strongly recommend this work to the atten- 

 tion of architects and professional engineers. There is not a 

 useless word in it from beginning to end. 



An Introduction to the Study of Fossil Organic Remains, espe- 

 cicdlij of those found in the British Strata: intended to aid 

 the Student in his Inquiries respecting the Nature of Fossils, 

 and their Connexion ivith the Formation of' the Earth. With 

 (10) illustrative Plates. By James Parkinson, Fellow of the 

 Royal College of Surgeons, Member of the Geological So- 

 ciety of London, the Wernerian Society of Edinburgh, and 

 of the Ctesarian Society of Moscow. 352 pages, 8vo. 

 The author of this useful little volume, well known by his 

 previous labours on the interesting branch of science embraced 

 in his title-page, in his preface dedicates the preiient pages 

 *' to the service of those admirers of fossils who have not yet 

 entered into a strict examination of the distinctive characters 

 of these interesting substances." 



In this sliglit but comprehensive sketch the author points 

 out, with more i)recision than he takes credit for, tlie difference 

 of lonns and structure in the numerous organized beings with 

 wliich the earth was peopled before the creation of man; 

 marking the several circumstances in which they agreed with, 

 or differed from, the inliabilants of the jjresent world ; and 

 points out, from the strata in which lliey exist, the order in 

 which they, prol)ablv, were f()rme(l ; avoiding however — indeed 



S 2 his 



