310 CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 
was usually attached to the pole of the tent, or else to the back of the post to which 
the standard barometer was fixed. 
Explanation of Table E. 
The results of the observations with the Standard Thermometer are contained in 
Table E., from page cxxii to cxxix inclusive. At pages cxxii and cxxiii are given the 
diurnal variation of the Standard Thermometer. The remainder of Table E. contains 
the mean results of the Standard Thermometer ; each set contains, in two lines, the 
mean hourly readings and the diurnal variation of the Standard Thermometer. 
Curves. 
The curves of the Standard Thermometer have already been noticed in speaking 
of the dry bulb. , 
Remarks. 
There is but one maximum and one minimum in the twenty-four hours, viz. at 2 
and at 18 hours. The oscillation or range varies, but the smallest is at Singapore, 
where the standard thermometer was placed inside the observatory, but exposed to a 
current of air passing through the building. The range was greatest at Moulmein 
and at Padang ; but as at these observatories the observations were taken under canvas 
only, the direct influence of the sun’s rays was very great. At Moulmein the tem- 
perature of the observatory was so hot as to be nearly unbearable, although the ther- 
mometer only reached 105° : at the commencement of the Introduction I gave a short 
statement of the materials with Avhich each observatory was constructed, that, in re- 
cording the height of the thermometer, the circumstances under which it was ob- 
served should be taken into consideration : the difficulty in tropical climates of ascer- 
taining correctly the temperature of the air is very great; the most difficult points 
to be determined appear to be ; the size of the building, the height of the roof and 
the nature of the materials of which it is composed, in order that the thermometer 
shall give only the temperature of the air, and not in addition that of the building 
in which it is placed. If the building is small, if the roof is low and of good con- 
ducting materials, such as slates or tiles, the thermometer is too high by day, and 
probably too low at night ; the only condition appears to be a lofty room, of large 
size, well-ventilated, and double-roofed with non-conducting materials. The observa- 
tories at Sarawak, Singapore and Batavia were excellent in this respect : at all other 
stations the thermometer was not sufficiently screened from the above liabilities to 
error, and therefore the daily curve at some of the stations is too high, whilst the 
mean temperature is nearly correct. 
Solar and Terrestrial Radiation Thermometers. 
In addition to these thermometrical observations, there was likewise in use, at the 
conclusion of the Survey, a Solar Radiation Thermometer, the bulb of which was 
