requisite for Meteorological Observations ^ ^c. 143 



suit. They would require to be unremittingly prosecuted, in 

 all variety of situations, and at the public expence. Proper 

 sets of meteorological instruments should be placed, not only 

 in the regular observatories, but sent to the different forts and 

 light-houses, both at home and at our principal foreign stations. 

 They might also be distributed among the ships employed in 

 discovery, or engaged on distant voyages. The cost of provid- 

 ing those instruments would be comparatively trifling ; and the 

 charge incurred, by conducting registers on a regular and di- 

 gested plan, might shrink almost to nothing in the scale of na- 

 tional expenditure *. 



The state of the barometer alone is now kept with tolerable 

 accuracy, because that instrument, being little influenced by 

 adventitious circumstances, marks nearly the same impressions 

 over a wide extent of surface. The thermometer, again, is sel- 

 dom observed at the proper hours, or in situations sufficiently 

 detached from buildings and solid walls. 



It is customary, for the sake of convenience, to note the 

 thermometer in the morning, at the height of the day, and 

 again in the evening. But these three observations must evi- 

 dently give results below the medium temperature of the whole 



• Government provided our discovery ships, sent to the Arctic seas, with 

 meteorological instruments ; but these, owing either to the ignorance or care- 

 lessness of the makers, were, in some instances, discovered to be very ineffi- 

 cient. Thus the thermometers were found to differ from one another ten de- 

 grees, and the Six's thermometers used for ascertaining the temperature of 

 the sea at different depths, were not trustworthy. In future experiments 

 with Six's thermometer, we would recommend correction to be made for the 

 effect of the compression of the water against the bulb, as had been carefully 

 done in Lord Mulgrave's voyage to those regions. Captain Parry carried out, 

 in his second expedition, two sets of hygrometers, photometers, and sethrio- 

 scopes ; but these instruments, it seems, were entrusted to the charge of the 

 astronomer, who either broke or neglected them. Yet a connected series of 

 observations, performed with such instruments in the Polar Regions, would 

 have furnished most important data for extending meteorological science. 



In a late philosophical voyage, directed to the Equator, some loose at- 

 tempts have been made to estimate the radiation from the sky. But what- 

 ever may be said of the theory of the sethrioscope, its great delicacy is 

 beyond dispute ; and for an observer to overlook or disregard such an instru- 

 ment, seems about as reasonable as if a navigator should prefer the old cross- 

 staff to the sextant or the repeating circle. 



