L. MECHANICS AND ENGINEERING. 485 



PRESERVATION OF TELEGRAPH POLES IN NORWAY. 



Telegraph poles in Norway are preserved from immediate 

 decay by introducing a solution of sulphate of copper into 

 holes bored into the freshly felled timber to a depth of five 

 or six inches, and plugged up with corks coated with tar or 

 varnish. The circulation of the sap, which goes on for some 

 time after the tree is cut down, tends to carry the solution 

 throughout the length of the pole, and impregnate the wood 

 thereby with it. The application is repeated two or three 

 times a year for several years, and the absorption of sulphate 

 in the course of this time is so great as to have a very appre- 

 ciable^eftect in increasing the durability of the timber. 1 A, 

 June 7,1872, 275. 



DEPARTMENT REPORT ON THE PREPARATION OF TIMBER. 



A valuable report has just been published by the Engineer 

 Department at Washington, as prepared by Captain T. J. 

 Cram, upon the decay of timber, and the methods for its 

 preservation for military and engineering purposes. The ex- 

 periments of Captain Cram have tended to show that, for a 

 limited period at least, creosoting the timber before immers- 

 ing it in sea-water is practically a preservation against the 

 attack of boring mollusks or crustaceans as well as ordinary 

 decay, the trial having now lasted, in some instances, for as 

 many as twenty years, without any apparent change in the 

 wood. 



This is in confirmation of the special report of the Academy 

 of Sciences of Amsterdam, upon experiments made by the di- 

 rection of the Netherlands government. Similar experiences 

 seem to have resulted from the creosoting of wood for rail- 

 road purposes, as well as for gun-carriages and other engines 

 of warfare. 



The report of Captain Cram discusses the general theory 

 of the application, and the methods of subjecting wood to 

 the desired treatment ; and it is maintained by him that its 

 application to breakwaters, government wharves, piers, and 

 other government constructions on the lakes, and on the sea- 

 coast, will result in an enormous saving of expense. General 

 Gil more, in an appendix to the report, expresses his opinion 

 that the Bethell process, with its American modification of 



