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Art. XV. ANALYSIS OF SCIENTIFIC BOOKS. 



L Philosophical Transactions of the Royal Society of 

 hondon^ for the Year 1825. Part II. 



The (irst paper in this Part of the Transactions is entitled, 



i. On the Effects of Tem'perature on the Intensity of Magnetic Forces, 

 and on the Diurnal -Variation of the Terrestrial Magnetic Inten- 

 sity. By Sam. Hunter Christie, Esq.,M.A. of Trin. Col., Camb., 

 Fel. Camb. Phil. Soc. ; of the Royal Military Academy Com- 

 municated by the President. 



The results of Mr. Christie's experiments upon the above subjects 

 are given in an extended series of tables, commencing with a tem- 

 perature of — 3° F., and terminating at 127°. From a tempera- 

 ture of 80°, the magnetic intensity decreased rapidly as the tem- 

 perature increased, and at above 100° a portion of the magnetic 

 power was permanently destroyed. But we shall not follow the 

 author into the details of his researches, in consequence of the 

 singularly fluctuating, yet progressive, state of magnetic science 

 at the present moment ; on another occasion we shall enter at 

 length upon the subject, and endeavour to do justice to Mr. Chris- 

 tie's labours. 



ii. The Croonian Lecture. On the Existence of Nerves in the Pla- 

 centa. By Sir E. Home, Bart., V.P.R.S. 



After complimenting Mr. Bauer on his microscopic infallibility, 

 Sir Everard proceeds to the enunciation of his discovery of pla- 

 cental nerves, a discovery " which he is proud to say was not the 

 result of accident, but of a regularly-arranged plan for that pur- 

 pose." 



That nerves are necessary for other purposes than mere sensa- 

 tion has long been admitted by physiologists, and it has been 

 proved by many well-devised experiments, that the processes of 

 secretion and growth of parts are under their immediate influence. 

 Mr. Bauer first detected them in the placenta of a seal, and after- 

 wards in the transparent portion of the chorion of the tapir, and 

 thence their existence in the human placenta, and a consequent 

 direct nervous communication between the mother and the child 

 was inferred, and afterwards proved. We think, however, that 

 these investigations are not yet sufficiently mature to warrant 

 the inferences that are drawn from them. 



