439 Dr. Henrys Analysis of a [June, 



different from those in use with us. These three are the cham- 

 pion, the oxnoble, and the kidney ; 500 parts of the recent 

 potatoe were employed in each experiment ; in the champion the 

 solid contents were 140 parts, of which 79*5 were starch, and 

 22 parenchyma; the oxnoble contains 132*5 parts of solid con- 

 tents, 111*5 of starch, and 23*5 of parenchyma; the kidney 

 contains 112*5 parts of solid matter, of which 82 are starch, and 

 22 parenchyma. 



The greatest proportion of solid contents in any of the species 

 is 165 parts in 500, in the variety which he calls the zelingen ; 

 and the least is 110 parts, in a variety called the marbled beau- 

 lieu. The largest quantity of starch is 119 parts in 500, in the 

 decrosilles, and the least in the parmentiere, being only 20*5 

 parts in 500. The parme»tiere, on the contrary, contains the 

 largest proportion of parenchyma of any of the varieties, being 

 94*5 parts in 500, while some of them contain no more than 20 

 parts. The author does not, however, profess to have arrived 

 at much accuracy in this part of his analysis, his attention hav- 

 ing been more particularly directed to the examination of the 

 substances contained in the water in which the pulp of the 

 potatoe had been washed. 



Article VII. 



Analysis of a Siliciferous Sub-sulphate of Alumine, found in 

 considerable Quantity in a Coal ISline near Oldham. By 

 William Henry, M.l). F.R.S. &c. 



Manchester, May 10, 1818. 



About a month ago I received from Mr. W. Chippendale, of 

 Oldham, in this county, a specimen of a substance which had 

 been found, the day before, in the old hollows or abandoned 

 works of the celebrated Black Mine, of which that gentleman 

 is one of the proprietors. Above the coal, he informs me, lay 

 a stratum, several feet thick, of a brittle, shivery stone, which, 

 on the removal of the coal, had fallen down and occupied its 

 place, it was on the surface of this fallen stratum that the 

 miners, on breaking into the hollows, discovered a bed, from one 

 inch to three or four inches thick, of a shining white substance, 

 which they represent as having, before it was soiled by rubbish 

 falling upon it, a singular and beautiful appearance. A consi- 

 derable quantity, mixed with the earth removed in re-opening the 

 ^ oiks, has already been sent out, amounting to several hundred 

 mds' weight ; and the workmen say that there is still a great 

 iit. 



The colour of this substance, when a mass of it is cut into, is 

 (■mediate between snow-white and milk-white, except in 



