466 Analyses of Books. {JUNE, 
Trott * . REP PL PS 9G 
INGOKEL | 54254 4S BEA oh 4 
100 
Dr. Wollaston’s mode of detecting nickel in iron is this. He 
dissolves a minute portion of the metal in nitric acid, evaporates the 
solution to dryness, lets fall a drop of ammonia on the dry mass, 
heats it gently to dissolve the oxide of nickel, draws the liquid to a 
little distance from the oxide of iron, and then adds some triple 
prussiate of potash. The appearance of a milky cloud indicates the 
presence of nickel. To determine the quantity of nickel he converts 
it into sulphate of nickel: 10 gr. of nickel form 44 gr. of sulphate 
of nickel. 
17. On Ice found in the Bottom of Rivers. By T. A. Knight,’ 
Esq. F.R.S. 
Mr. Knight observed upon a mill-pond in the river Teme, in 
Herefordshire, millions of little frozen spicule floating on the sur- 
face of the water. At the end of this pond the water fell over a 
low weir, and entered a narrow channel, where its course was ob- 
structed by points of rocks and large stones, By these numerous 
eddies were occasioned, which drew the floating particles of ice 
under water. These particles striking against the stones at the 
bottom of the river, adhered to them; and in this way a quantity 
of ice accumulated at the bottom of the river; and had the cold ~ 
continued, it would no doubt have covered the whole bottom. 
18. On the Action of the detached Leaves of Plants. By T. A. 
Knight, Esq. 
Mr. Knight had formerly given it as his opinion that the matter 
which becomes vitally united to trees previously passes through 
their leaves. The object of this paper is to state fresh evidence in 
proof of this opinion. Pieces of bark separated from the branch of 
a vine, and attached only to the foot stalk of a leaf, continued to 
vegetate, and to increase in bulk, as if they had been attached to the 
tree. Leaves of the potatoe planted in pots, and regularly watered, 
continued to vegetate till winter ; and when pulled up, the bottom 
of the foot stalk had swelled out, and consisted of matter similar to 
the tubers of the potatoe. A branch of the vine being cut off, and 
laid horizontally, with part of each mature leaf dipping into a bason 
of water, the immature leaves, and the extremity of the branch 
continued to grow and elongate. 
19. On the Manufacture of the Sulphate of Magnesia at Monte 
della Guardia, near Genoa. By H. Holland, M.D. F.RS. 
The mountain of Guardia is composed of clay-slate, over which 
lie beds of serpentine and magnesian lime-stone, in which occur 
veins of iron and copper pyrites, obviously mixed with matter con- 
taining magnesia. A manufacture was originally established to ex- 
tract blue and green vitriol from these pyrites; but the appearance 
of sulphate of magnesia during their processes induced the pro- 
