4/0 Hints for the Formation of 
wlio study meteorology, as well as geology, ought to be 
furnished also with an hygrometer and an electrometer. 
12. For ascertaining the temperature of the sea, at 
great depths, it will be necessary to have a thermometer 
constructed like that described in my Travels through the 
Alps :* for lakes, an apparatus like that pointed out in 
the note of Section 1399, will be sufficient. 
13. Those who understand a little geometry, ought to 
provide themselves with a sextant, having an artificial 
horizon, and also a chain, in order that they may be able 
to measure a base, and thus take the altitude of an inac- 
cessible peak, the breadth of a river, &c. &c. With this 
sextant they may also find the latitudes. In regard to 
the longitudes, they require, besides instruments, an ex- 
pertness in this kind of observation, winch cannot be at- 
tained but by mariners or professed astronomers. 
14. It will be necessary also to have within reach tools 
for repairing an instrument in case it should happen to be 
deranged; such as pincers, files, tnrascrews, compasses, 
gimblets, wire, needles, thread, and packthread. 
15. Lastly, some good map, pasted on canvas, of the 
country you propose to examine ; and this map ought fre r 
quently to be compared with your itinerary, and the bear- 
ings given by your compass. 
16. In regard to the care required for the traveller’s 
person, be must have a light dress made of cloth, w ithout 
lining, of a white colour, as well as his bat, that he may 
be less exposed to the heat of the sun’s rays; with jack- 
ets, some cool for the warm regions and the vallies, and 
the other warm for the cool regions and eminences ; a 
good great coat; green spectacles, and a black crape, to 
secure the eyes and face from the snow. Lastly, if he is 
to pass the night in the open air, a tent or cannoniere , a 
bear’s skin to sleep upon, and woollen blankets. 
Section 1392, Plate 1, 3 
