MECHANICS AND USEFUL ARTS. 53 



PYROLIGNITE OF IROX. 



In the proportions adopted by the writer, viz., 1 part of pyrolignite to 6 parts of 

 water cost of pyroliguite, 23 cents per gallon. 



Labor at tank, etc., . . . .... 1-0 cent. 



Solution absorbed, 6-5 " 



Cost per sill, 7.5 



The writer does not claim that this method of impregnating timber by 

 capillary attraction is superior to any process extant, for such an assumption 

 at this period would certainly be premature and somewhat arrogant. The 

 question of its efficacy hangs upon a single point, which is this : Does it intro- 

 duce a sufficient quantity of the preservative solutions to produce the desired 

 effect? From the mass of data condensed in the tables given above, it 

 appears that the average degree of absorption varies in the different classes 

 of woods. The average of the sills impregnated in the tanks range from 

 - 52 1 to 0'78 * of a gallon per cubic foot. The averages of the timbers in the 

 cistern, from 0'53 1 to I'lO 1 of a gallon per cubic foot. 



OX THE CONNECTION BETWEEN THE STRUCTURE AND THE PHYS- 

 ICAL PROPERTIES OF WOOD. BY PROF. KNOBLAUCH. 



The author seeks to ascertain whether any connection is ascertainable be- 

 tween the structural relations of various kinds of wood and their observed 

 physical properties, such as their powers of resonance and conduction of 

 heat, etc., in the same way as was done for one and the same wood by 

 Savart in respect to resonance, and more especially by Tyndall in respect to 

 the conduction of heat. 



The primary object was to trace the difference in the conduction of heat 

 shown by different woods, according as the heat has to traverse the wood 

 in a direction parallel with, or at right angles to, the direction of the grain. 

 For this purpose, slabs of the woods to be examined were bored through, 

 perpendicular to their planes, and then covered as uniformly as possible with 

 a coating of stearine. A hot wire, exactly fitting the bore, was introduced 

 into the latter, and continually turned round during the experiment. By this 

 means the coating of stearine around the orifice was melted; but, as we 

 should expect, not in concentric circles, but in elliptic zones, whose major 

 axes invariably coincided with the direction of the grain. The great differ- 

 ence in the behavior of different kinds of wood (about eighty sorts Avere 

 examined) under these circumstances is at once apparent. With some, the 

 ellipses are tolerably circular; by others, more elongated; while by others, 

 again, the major axes are so extended as to be nearly twice the length of 

 the minor ones. The eccentricity of these ellipses, which furnished a graph- 

 ical expression for the conductive power of the wood in the directions be- 

 tween which the structural difference was greatest, made it possible to divide 

 the different kinds of wood into four distinct groups. In the first, the ratio 

 of the minor to the major axis of the ellipse is on the average as 1 to 1/25. 

 To this group, Acacia, Box, Cypress, King-wood, etc., belong. In the sec- 

 ond, and by far the most numerous group, containing Elder, Xut,- Ebony, 

 Apple, several dye-woods, etc., the mean value of this ratio is 1 to T45. In 

 the third group, to which Apricot, Siberian, Acacia, Brazil-wood, Yellow- 



* American gallons. 



5* 



