On the Dry Rot. 16& 



such delicacy as to revolve by the earth's magnetism. Placed 

 upon the top board of the machine, the connexions being made, 

 it revolves rapidly by the attractions and repulsions of the upper 

 poles of the large magnets underneath. 



A small electro-magnet, charged by the three inner coils of one 

 of the armatures, sustained permanently ten pounds, while the 

 machine was in action. 



Fusion of iron filings. — When a wire from one pole of the 

 machine was placed in a heap of fine iron filings, and a bunch of 

 these raised by a magnetic bar connected with the other pole, 

 the connecting shreds of filings, sometimes an inch in length, be- 

 came intensely ignited throughout, fused into a mass and fell off, 

 leaving frequently a globule attached to one of the poles, which 

 glowed for a time after the contact was broken, and then ex- 

 ploded, as is seen with particles of iron burning in oxygen. This 

 curious experiment succeeds best, when the filings are held be- 

 tween two opposite poles of magnetic bars, connected each with 

 the poles of the battery. 



Art. XV. — On the Dry Rot ; by Phinehas Rainey. 



Middletown, (Conn.) March 22d, 1838. 



TO PROF. SILUMAN. 



Sir — Permit me through the medium of your very Valuable 

 and widely circulating Journal, to lay before the public the fol- 

 lowing facts and observations in relation to the dry rot in timber. 



It is matter of history, that the timber of the ancients lasted 

 some hundreds of years longer than that of the moderns, and 

 there is no record that their timber was subjected to any artificial 

 process to make it durable. It is therefore probable, the reason 

 why the dry rot exists to such an alarming extent in the heart- 

 wood of the timber of the present day, is to be found in the sea- 

 son of cutting the trees. It is probable that the present general 

 practice of cutting timber in the winter was avoided by the an- 

 cients, and that it originated in England, when the botanical 

 theory, that the sap of trees is in their roots at that season of the 

 year, was first promulgated. 



YoL. XXXIY.— No. 1. 22 



