des Agens Physiques sur la Vie. 133 



are indeed somewhat appalling, but his clear ^nd distinct 

 metliod of arrangement greatly facilitates the reader's endea- 

 vours to master the extensive subjects of his pages. As a 

 book of reference it should find a place in the library of 

 every scientific society, and no individual devoted to philo- 

 sophy should omit the possession of it. 



The agency of the air around us, water, and heat and 

 cold, have often been the objects of chemical inquiry, from 

 their known great influence upon the animal economy. The 

 changes effected by the phenomena of animal life upon these 

 agents liave been accurately examined, and partly reduced 

 to a mathematical precision of calculation. 



Spallanzani and others have viewed the subject as it 

 regards physiology, but with such results as left the field 

 open to subsequent investigation. Dr. Edwards seems ta 

 have seized upon the deficiencies of his predecessors, andy 

 by going over their ground, and extending his own in- 

 quiries, he has arrived at most interesting and important 

 results. These he has divided into four parts, as they relate 

 to the different orders of the animal creation. The first part 

 includes some of the lower animals, particularly tenacious of 

 life, and of cold blood, such as frogs, toads, and salamanders* 

 The second part is devoted to other animals of cold blood, 

 and of the vertebrated order, as fish, and those reptiles which 

 include lizards, snakes, and turtles. The third part refers to 

 warm-blooded animals ; and the fourth part of the work i^ 

 dedicated to the influence of the physical agents upon thei 

 human race and vertebrated animals. To these the author 

 has added the discoveries of modern times, relative to elec- 

 tricity on the animal economy, in an Appendix. A collection 

 of tables is appended to the work, exhibiting the principal 

 series of his experiments, as they regard the relative influence 

 of physical agents on the duration of life, and the plienomena 

 resulting from their mutual action. 



The great importance of the four grand divisions of thei 

 work forbids our hastily reviewing them, and we will endea- 

 vour to condense so much of the information they contain as 

 may forward the objects of our analysis. Dr. Edwards thus 

 announces the arrangement of his work : — ; 



" Ces recherches auront done rapport k I'air dans les conditions 

 de quHtitite, de niouvement et de repos, de densite et de rart'fac-* 

 tion; a I'eau liquide et a la vapeur aqueuse; a la temperature, 

 dans ses moditications de degre et de durtje; a la lumiere et ^ 

 Telectricite. Ces causes agissent a la fois sur reconomie aniraale, 

 Qrdinairem^nt d'uue maoi^re sourde et imperceptible ; et toujours 



