THE TUADE IN COPROLITES. 103 



beams, wale planks, and stringers, Mr. Watson considers it unrivalled. It 

 takes the steam well, and there is no fear of its spauling in working round 

 a full bow. 



The average breaking weight of blue gum seasoned twenty years was 

 1,225 lbs., and the direct cohesion upon the square inch 21,667 lbs. seasoned 

 one to five years, 975 lbs. breaking point, and 27,839 lbs. cohesion. 



lbs. lbs. 



Stringy bark (seasoned) 974 21,140 



Ditto, green 734 21,057 



Swamp gum, seasoned (inferior) 914 16,888 



Ditto, green 719 18,488 



The elasticity of thoroughly seasoned blue gum is a half greater than 

 that of teak and moorung saul ; double that of peon, ash, English oak, and 

 red pine ; three times greater than that of pitch pine, Dantzic and Adriatic 

 oak ; and five times greater than that of elm. 



Swamp gum is the largest of the Eucalypti. A tree measured by Mr. 

 Mitchell was 87 feet in height to the first branches, and 21 feet in circum- 

 ference at eight feet from the ground. A second was 213 feet in extreme 

 height, and 18^ feet in circumference at ten feet from the ground ; and a 

 third was 251 feet. But these are dwarfs compared with others, and some 

 of the blue gums on the southern coast and on Maria Island. This 

 wood is lighter and of opener grain than the blue, from which, by a casual 

 observer, it is scarcely distinguishable, and is preferable for spars, although 

 subject to cracks. By some it is considered equal to ash, and hence is 

 sometimes called ash-gum. 



Stringy bark shrinks, and is liable to rents, but yield spars of the largest 

 size. A sound tree of this variety, in the vicinity of Cam River, a mile or 

 two from the coast, on the north side of the island, measured by Mr. 

 Mitchell, was 200 feet in height, to where its trunk had been broken off, 

 and was 64 feet in girth at four feet from the ground. Its specific gravity 

 is under 1,000. 



THE TRADE IN COPROLITES. 



BY THE EDITOR. 



Coprolites are the exuviae of extinct animals, but in the commercial 

 meaning the name includes also bones, teeth, and other fossil relics of animals. 

 Containing much phosphate of lhne, they are used for making superphos- 

 phates. When ground to powder in a mill, and acted on by sulphuric acid, 

 a part of the phosphoric acid is liberated, and a more soluble compound ob- 

 tained. But little is known on this subject, and no lengthened details have 

 yet been published that we are aware of. It is chiefly in the counties of 



