190 Mr. Wollaston's description of the 
may be fastened down by screwing the thermometer into the 
boiler ; or, which is better, by a separate collar U for the pur- 
pose, to screw into the boiler, having the same internal screw 
above to receive the thermometer. This conical cap has a 
wire soldered round it at V WX, and on this wire turn by eyes 
at their ends seven wires, nine inches long and of sufficient 
strength. They are placed at six equal distances round the 
cap, two of them being placed close together. These wires by 
bearing on the ring ST are spread outward, and being con- 
nected by gores of thin linen, sewed between them from 
top to bottom, are prevented from spreading beyond a cer- 
tain point and form a very steady base for the support of the 
whole instrument, and at the same time a bell tent to protect 
the lamp and boiler from the wind. The two wire legs, which 
are placed together, are not connected otherwise than by a 
hook at bottom, and will allow the tent to be opened at that 
part for examining and adjusting the lamp, while the instru- 
ment stands firm on the remaining legs. The lamp (fig. 6.) 
is a cylinder 1,8 in diameter, and 0,9 deep, having a tube in 
the centre to carry a wick, and a cover with six holes round 
it of OjS diameter each, and an opening in the middle 0,8 
diameter; a copper pipe, 0,85 in diameter, and 1,1 long, turns 
over the opening by means of a hinge, and forms a chimney 
to prevent smoke, on the principle of Argand's lamp. I burn 
oil with a quantity of tallow added, to make it congeal. The 
lamp has a rod of strong wire fixed to its circumference 
within, and sliding in a tube YZ on the outside of the boiler. 
Fig. 7. represents the instrument on its stand for use. 
To pack the instrument for carriage, the thermometer is 
secured by being screwed into its upper and under caps, and 
