Himacayva Mountains. 207 
severe that we were obliged to keep fires in our small tents, while on the 
out side our ink was frozen, and unluckily we did not think of the precau- 
tion of keeping the circle as nearly as we could at an even temperature, by 
leaving it on the out side of the tent when we had read off the angle. On 
the contrary, as soon as we had observed the meridian altitude of a star, and 
registered it, we laid down the circle in the heated tent, until it was time to 
take another star, and as that operation necessarily took up some time, the 
limb and verniers being of different sorts of metals, might possibly expand 
and contract in contrary and uncertain dircetions, and cause error. Such 
may, or may not be the cause, and in justice to the instrument I state these 
circumstances, though I should think there is no need to make suppositions, 
which may appear forced, when it is considered, that the radius of the 
reflecting circle is only six inches, and that exact reading by candle light 
is not to be expected, and that there is a great difference between observing 
calmly in the plains, and on the ridge of a stormy mountain, 11,529 feet 
above their level. At Bairdé also the temperature differed from that at 
the Chir and Sehdranpir ; to say nothing of the possible uncertainties of 
celestial refractions on the two mountains, 
For observing the eclipses of Jupiter's satellites, and thence determining 
the longitude of the first meridian, I used an achromatic refracting telescope 
of forty-two inches focal distance, and 2-7 inches aperture: it was 
made by Dotionp, and had rack work and every adjustment. It was my 
own property. Lieutenant Herserr used one of the same dimensions, be- 
longing to government, it had no rack work, but was a good instrument, 
and also made by Dotuonp: he had also a good chronometer, public pro- 
VOL. XIV. 3G 
