58 



Many experiments have yet to be made before we arrive at a knowledge of the cheapest 

 and best preparation for the preservation of timber. 



The essential desiderata are — the expulsion of the sap from timber, the conversion of its 

 soluble to insoluble portions, and the closing up, as far as practicable, of the sap vessels. 

 The salts most economical and at present usually applied contain an excess of sulphuric 

 acid. If it be not present to excess, it should be added, as before remarked, for it is to its 

 coagulating property, exerted on caseous or albuminous portions of timber, that its efficacy 

 chiefly depends. The metallic sulphates, if costs are to be taken into the estimate, are 

 therefore preferable to any other with which experiments have hitherto been made. 



Soaps from the metallic, earthy and alkaline salts have not, so far as my knowledge 

 extends, been tr4ed. I am now experimenting on some of them and believe they may be 

 as useful for the preservation of timber as any other substance whatever, and they can cer- 

 tainly be applied at a much less expense than any other with which I am acquainted. lint 

 with these wo must become further acquainted before we can determine their real value. 



If the process of M. Boucherie be adopted and timber which has been previously 

 charged with sulphate of iron be subjected to his water-tight sack apparatus, filled with an 

 aqueous solution of quicklime, in such manner as to coerce its passage through its sap 

 vessels, we shall have a compound of sulphate of lime and prot-oxide of iron formed at once 

 in them, and perhaps at a cheaper rate than any other that can be devised. 



It was my intention to have dwelled somewhat upon the best practical modes for coloring 

 timber, but I have already much exceeded the limits which I had prescribed for the discussion 

 of this and the other subjects proposed. I shall, therefore, be compelled to omit its consi- 

 deration for some future occasion. 



With this knowledge in respect to making a proper selection and preservation of timber 

 before him, the ship and wharf builder, the carpenter and farmer, have it in their powev 

 to render their building and fencing materials very durable, almost imperishable, and that, 

 too, if the importance of the measure be properly regarded, at a very inconsiderable expense^ 



This subject is particularly worthy the attention of our govermnent, both in respect to 

 the treatment of timber designed' for the construction of ships and piers, and also for the 

 preservation of vessels of war when laid up in ordinary. 



In time of peace, it will be generally conceded that a national marine composed of small 

 war vessels answers equally well numerically as the larger classes of sliips for the naval 

 service, while they are maintained at a much less relative expense. If this be correct, ar.d 



