THE DURABILITY OF MATERIALS. 



571 



control. Not so with such as is imported 

 either from America or the Baltic ; nor is 

 r-it ever likely that we will have the felling 

 of it in either place regulated by the 

 rules we would wish to lay down. 



Of the various remedies recommended 

 for the preservation of this useful article, 

 may be noticed that of M. de Gemini, 

 recently detailed in a Memoir laid by the 

 Minister of Marine before the Academy 

 of Sciences of Paris. The report upon 

 this subject, drawn up by MM. Boussin- 

 gault, de Gasparin, and Decaisne, states 

 that M. Gemini was of opinion that me- 

 tallic salts introduced into the wood had 

 the effect only of impregnating it with 

 substances more or less soluble, or even 

 volatile, w T hich consequently could not 

 remain long in the wood ; and that by 

 introducing it by force of machinery, 

 the fibres became separated, and the wood 

 rendered even more liable to decay than 

 if left in its natural state. 



The three gentlemen above mentioned 

 differ from M. Gemini in this matter, and 

 declare that the salts have not the effect of 

 disorganising the woody fibre, and also that 

 the combination of metallic salts with wood 

 is not so fugacious as M. Gemini asserts. 



M. de Gemini's process is thus described 

 in the Gard. Chron. — " He operates on dry 

 wood, or on what has been dried in his 

 apparatus, which consists — 1. Of a cast-iron 

 hollow cylinder, destined to hold the pieces 

 of wood, and sufficiently strong to resist 

 the effects of a vacuum within. One of 

 the ends of the cylinder has a close cover, 

 secured by screws after the wood has been 

 introduced ; the other is furnished with a 

 valve, opening progressively by means of 

 a screw, and serving to reintroduce the 

 air to the cylinder. 2. Three reservoirs 

 for the solutions. These are placed in the 

 ground under the cylinder, with which 

 each is in communication by a pipe hav- 

 ing a stop-cock. 3. An air-pump for pro- 

 ducing a vacuum in the cylinder. 4. A 

 force-pump for injecting the liquids with 

 great pressure into the cylinder. 5. A 

 generator, intended merely to fill the cylin- 

 der with steam by a communication pipe." 

 This apparatus resembles, in some de- 

 gree, that of Breant, afterwards improved 

 by Payne, and employed in England, for 

 several years, for impregnating timber 

 with bituminous substances. The injec- 

 tion used by M. Gemini is tar, or tar and 



pitch, for some purposes, while he uses 

 solutions for others. We apprehend that 

 the former is used for timber of a soft 

 nature, and having large pores, while the 

 latter is used for more matured material, 

 and the harder or closer-grained woods. 

 He appears to have fallen into the same 

 mistake as M. Boucherie did many years 

 ago — namely, endeavouring to inject two 

 solutions, the one after the other, without 

 considering that, if his first solution was 

 injected to the extent of filling all the pores 

 of the wood, the effect of the second would 

 be to drive that out to make room for itself. 



So far, however, as M. Gemini's theory 

 goes, we believe that it is useful so far as 

 charging the alburnum or sap-wood with 

 pitchy matter is concerned. How much 

 farther his invention is useful does not so 

 clearly appear. 



In regard to the qualities of timber used 

 in hothouse architecture, they stand as 

 follows : — Memel, brought from Prussia, 

 in the Baltic ; Riga, from Russia ; Dantzig, 

 from Western Prussia ; redstone pine, 

 from Miramichi, in North America j and 

 yellow pine, from Quebec. 



§ 11. — ON THE DURABILITY OF 

 MATERIALS. 



The durability of materials depends on 

 their natural fitness, or the degree of perfec- 

 tion to which they are brought artificially. 



Thus bricks can never almost be over- 

 burnt ; and, at the same time, there are 

 certain kinds of clay or brick-earth much 

 better for the purpose of making them 

 than others, and which will stand for ages, 

 even if not burnt to a blue or slate colour. 

 The principal fault of bricks used in Scot- 

 land is, that they are neither well formed 

 nor well burnt — a circumstance arising 

 naturally out of the fact that Scotland 

 abounds in stone of first-rate quality ; and 

 indeed, till lately, very few bricks were 

 made, and those chiefly for furnace-work, 

 inside walls, and lofty chimneys. We 

 have the satisfaction to know that, through 

 the liberality of the Duke of Buccleuch. 

 we introduced the making of bricks upon 

 the London principle, about fourteen 

 years ago, into Scotland. The demand 

 since, for railway purposes, has much im- 

 proved their manufacture. 



" The most durable of all walls are 



