334 



CURVILINEAR SAW. 



Jtestoration of 

 magnetism to 

 an oxide not 

 the effect of 

 caloric, 



for it taVcs 

 place without 

 heat. 



Whether oxi- 

 gen may weak- 

 en magnetism 

 is not determin- 

 ed. 



Now let us continue to subdivide this particle, till the dis. 

 tance between the two poles of its molecules, brought into 

 contact with the needle, shall be so small, that the seats of 

 the two poles shall be as we may say compounded together : 

 the difference between the attraction and repulsion will then 

 become inappreciable, and the molecule will give no signs 

 of magnetism. 



It may be said, that this development of magnetism in 

 oxides strongly heated is rather owing to the action of the 

 heat weakening the coercive power that opposes the mag- 

 netism. But beside that this coercive power is not a fact 

 so certain as the approximation, that these oxides undergo 

 whenever they become magnetic, it can account only for 

 part of the phenomena, since in oxides by precipitation, 

 which can be obtained magnetic at pleasure, heat has no 

 concern. 



For the rest, whatever be the cause of this phenomenon, 

 it is proved, that oxides saturated with oxigen are magne- 

 tic, or at least may become so without losing an atom of 

 oxigen. I do not however mean to assert, that a given 

 quantity of iron saturated with oxigen retains the same 

 magnetic power as it possessed before it was oxigenized : 

 for on this subject I have made no experiments. 



IV. 



Description of a Curvilinear Sazc , invented by John Trotter, 

 Esq. , of Soho Square, from whom the following Cam* 

 munication was received*. 



ENT^EMEN, 



A curvilinear "^7^7' 

 saw very desira- V V 

 hie 



1TH the view of obviating many difficulties and ex- 

 penses, which have long attended the operations of those 

 requiring curvilinear sawing in their trade, and of public 

 bodies connected with those 1 trades, through the licentious 

 and refractory conduct of sawyers, it has been represented 

 to me as a measure extremely desirable, to adopt more ge- 



* From the Transactions of the Society of Arts, &c. for 1806, whQ 

 voted their gold medal to Mr. Trotter for this invention. 



nerally 



