W. P. Headden — Products found in an old Furnace. 93 



Art. XI Y. — Some Products found in the Hearth of an Old 

 Furnace upon the dismantling of the Trethellan Tin Works, 

 Truro, Cornwall /* by Wm. P. Headden. 



The suite of samples forming the subject of the following 

 notes was presented to the writer by Dr. Richard Pearce of 

 Denver, who states that they were obtained from the hearth of 

 an old furnace in the Trethellan Tin Works at Truro, Corn- 

 wall. The furnaces had been idle for a short period prior to 

 the abandonment of the works, which took place about 1872, 

 but they were not dismantled until 1892, and it was at this date 

 that the samples were obtained. These furnaces had been in 

 use for at least sixty, and probably for nearly a hundred years. 

 The ores smelted in them were the usual Cornish tin-ores carry- 

 ing some arsenopyrite. Dr. Pearce showed, in an article pub- 

 lished in 1871, that this arsenopyrite is cobaltiferous, and this 

 is probably the source of the cobalt found in the samples. 



Stannous Sulphide. — This compound occurred as black, 

 highly lustrous, monoclinic crystals covering a slag surface to 

 the thickness of nearly a quarter of an inch. The forms 

 made out were 111, 111, 110 and 010. The crystals are tabu- 

 lar, owing to the development of the clinopinacoid ; the lustre 

 is strongly metallic. The crystals are invested with small 

 globules of metallic tin, invisible to the naked eye, but which 

 appear rather abundantly when the crystals are examined under 

 the microscope. The stannous sulphide does not rest immedi- 

 ately upon the slag, but upon a stratum of another crystallized 

 compound, which also appears, but in somewhat isolated groups, 

 through the mass of stannous sulphide crystals. 



Crystals which proved to be the same in composition were 

 observed occurring sparingly in the upper part of another mass 

 of crystals.an inch, or perhaps more, in thickness; these were 

 much smaller and were quite free from tin. The analytical 

 data on which the identification rests are analyses of these 

 two specimens. In the latter case, 1*78 per cent insoluble has 

 been deducted, and the remainder calculated to a hundred, 

 when the analyses give the following composition for the 

 crystals : 



Per cent. Atomic Equivalent. Atomic Ratio. 



Sn 71*538 6063 ) 



Fe 4-881 8-71 [ 70'05 1-00 



Cu 0-452 -71 ) 



S 23-129 72-27 72*27 1-03 



100-000 



* Abstract of an article read before the Colorado Scientific Society, Nov. 6, 

 1897. 



