Chemistry . 397 
’ Mr E. Hitchcock observed, at Deerfield, in Massachussets, 
in 1812 or 1813, cylinders of snow similar to those above de- 
scribed by Mr Clark, and formed under similar circumstances. 
None of the cylinders, however, were more than six or eight 
inches in diameter . — American Journal of Science, voh ii. No. 1. 
p. 132. and vol ii. No. 2. p. 375. 
II. CHEMISTRY. 
14. DanielVs New Platinum Pyrometer for High Temperatures . 
—The only pyrometer for high temperatures which has hither- 
to been used, is that of our late eminent countryman Mr Wedge- 
wood, which was founded on the principle, that clay contracts in 
bulk, in proportion to the intensity of the heat which is applied 
to it. The difficulty, however, of obtaining clay pieces of uni- 
form composition, and the discovery that the same degree of 
contraction may be obtained by the long continuance of a low 
temperature, and the short continuance of a high one, have pre- 
vented this instrument from coming into general use, and have 
thrown an uncertainty over the results given by Mr Wedge- 
wood. 
The new pyrometer invented by Mr Daniell is very simple in 
its construction, is easily repaired when injured, and will extend 
the scale of the thermometer at least to the fusing point of cast 
iron. It distinctly indicates a change of about seven degrees of 
Fahrenheit’s scale. 
The instrument consists of a bar of platinum 10J inches long, 
and 0.14 of an inch in diameter. It is placed in a tube of black 
lead earthen ware, and the difference between the expansion of 
the platinum bar, and the earthen-ware tube, is indicated up- 
on a circular scale, in consequence of a fine platinum wire T J 0 th 
of an inch in diameter, which is fixed to the end of the platinum 
bar, and is coiled three or four times round the axis of a small 
wheel, which we shall call A, fixed at the back of the circular 
scale. The other end of the small platinum wire is bent back, 
and attached to the extremity of a slight spring which keeps 
the wire in a state of extension. The axis of the wheel A is 
0.062 of an inch in diameter, and the wheel itself is toothed, and 
plays in the teeth of another smaller wheel a , whose diameter is 
VOL. V. NO. 10. OCTOBEE 1821. D d 
