148 PLATINA SPRINGS FOR tVATCHRS. 



inconvenience so often complained of in crowded shops ami 

 manufactories, where so many people are forced to breathe 

 the same air over and over again, and which really is injurious 

 to a very great degree. I say it will remedy this by purify- 

 ing the air. I have no doubt it will completely hinder any 

 thing like fever from spreading in those shops and manufac- 

 tories, if it should be accidentally introduced. In fact it 

 will be found to purge and purify the air, and to promote 

 health, instead of injuring it. 



I am, Sir, 



Your humble servant, 



B. COO&. 

 Caroline-street, Birmingham, Dec. 27 th, 1808. 



IX. 



On the Superiority of Platina for making the Pendulum 

 Spring of Watches. By Mr. James Scott. 



To Mr. NICHOLSON. 

 SIR, 



Balance spring -OlS your valuable Journal is universally esteemed a source 

 capable of im- f t ne best information and most general utility to the me- 

 chanical as well as the philosophical world, I beg leave to 

 trouble you to insert a few remarks on the subject of the 

 pendulum spring, as it is a part of watch work I have often 

 considered capable of the greatest improvement. 

 Platina the * nave keen l° n S C0I >vinced of the superior advantages of 



best material, platina over any other metal of which this instrument has 

 hitherto been made, but I have not until lately been able to 

 procure any of it in wire fit for that purpose. I find it by 

 repeated experiments to possess great superiority on account 

 but arsenic °^ ' ts inperceptible expansion ; and, what is worthy of re- 

 must not be mark, the platina procured for this purpose should not be 

 consiwalin 1 consolidated by arsenic, as it is by that means liable to ex- 

 it, pansion. I also find it, when properly drawn, to possess 

 sufficient elasticity for any extent of vibration ; it coils ex- 

 tremely well ; and, if placed when coiled on the surface of 

 a flat piece of metal, making one end of the spring fast, and 

 marking exactly the other extremity, the slightest expansion 



