Daniell's Meteorological Essays. 225 



scures its illuminated surface. We state this result, inasmuch 

 as it completely disproves the reasoning founded on a late ex- 

 periment made in this country, by which it was attempted to 

 be shown, that the lunar light was capable of affecting a very 

 sensible differential thermometer. 



Besides the irregular fluctuations in the altitude of the ba- 

 rometer, a patient and careful investigation shows that there is 

 a horary oscillation*, apparently produced by tides in the at- 

 mosphere. By a series of observations, at seven different sta- 

 tions, one extreme being under the equator, and the other in 

 50 degrees north latitude, it appears, that while the irregular 

 movement of the atmosphereand general range of the barometer 

 increase, in going from the equator towards the fifty-second de- 

 gree of north latitude, there is a regular concomitant fluctuation, 

 that augments as we proceed from the higher latitude towards 

 the equator. According to an hypothesis laid down by our 

 author, there must be a latitude, where the causes that pro- 

 duce the tides will just be in equilibria ,• and in latitudes still 

 higher the fluctuations will be in an opposite direction. In 

 support of his theory, he adduces the register of the barometer 

 kept in the second northern expedition, and compares it with 

 that kept by Major Long's party during the same season. It 

 may truly be said, that no step in science is unimportant, and 

 that trivial circumstances may frequently produce great good; 

 for we thus see distant observations, taken by scientific men of 

 different nations, and without any previous concert, made use 

 of in the investigation of a subject, that had probably not oc- 

 curred to the minds of either of the observers, at the time of 

 instituting their experiments. In the new expedition that is 

 about to sail from England, to pursue the discoveries on the 

 northern shore of the American continent, this subject will be 

 made a special matter of research : to furnish the means of 

 comparison, simultaneous observations will be made in Lon- 

 don, and arrangements have been made by the British Board 

 of Longitude, to place a similar set of instruments in Colum- 

 bia College in the city of New- York. In this way, four sets 

 of observations will be made, viz. at London ; at Hammerfest, 

 near the North Cape of Europe, where corresponding instru- 

 ments have been sent; at New- York ; and at Prince Regent's 

 Inlet ; these observations will be made under two different me- 

 ridians; that of London being the same with that of Ham- 

 merfest, and that of New-York with Prince Regent's Inlet. 



In making a series of meteorological observations, the regi- 

 ster will be of little importance, unless the instruments be of 

 good quality, and much attention be given by the observer 

 * Essay 4th. 

 Vol. 64. No. 317. Sept. 1824. F f himself 



