Preservation of Mine Timbers 315 



quently been observed in the case of copper sulphate. So far, it 

 has not been shown for corrosive sublimate and sodium fluoride. 

 Too rapid a washing out of the salt from the wood (we can 

 never absolutely prevent washing out because an entirely insolu- 

 ble salt would also be entirely useless) can best be avoided by 

 using as deeply penetrating a treatment as possible, such as is 

 given by the employment of vacuum and pressure in closed 

 cylinders. Painting of the wood or mere dipping for a few 

 minutes are therefore under all circumstances to be discarded. 



The Austrian Telegraph Company, years ago, made voluminous 

 comparisons of treated and untreated wood. Trials made upon 

 about 1,000 telegraph poles showed irrefutably that painting had 

 not had the slightest influence upon the life of the wood. 



The harmful effects of creosote have already been considered. 

 It may be added that for coal mines, moreover, the increased 

 inflammability of the wood due to the use of creosote is not 

 inconsiderable. From the methods of treatment with salts, which 

 come into consideration in mine timbers (Kyanising and Wohl- 

 mann's mixture), there are no especially harmful effects upon the 

 health of the workers to be feared. During the process of treat- 

 ing, such precautions as are required with the material used must, 

 of course, be taken. The only objection to either salt is that the 

 skin of the hands becomes brittle and cracked. It has been 

 established in practice as fully sufficient a protection, if the 

 hands of the men engaged in the treating are well greased with 

 vaseline. 



That the wood shall not suffer from the treatment is so self- 

 evident that it does not require any further discussion. As a 

 matter of fact, however, not a few of the materials used for 

 treating wood attack the wood fibres very seriously and thereby 

 greatly reduce the strength of the wood. In the case of sodium 

 creosote, which was formerly much used in lignite mining, the 

 timbers became in the course of five or six years so brittle from 

 the excess of free sodium hydroxide that they broke under a 

 load. Famous in this respect is the Hasselmann method. Under 

 the influence of the high temperatures at the time of treatment 

 the salts used by Hasselmann dissolved the lignified portions of 

 the wood and changed the wood into a horny mass. This is, 

 however, nothing but cellulose. Hence in the fungus cellar, 

 timbers treated by Hasselmann's process have retained their form 



