244 Address of the President of the British Association. 



" The doctrine of the influence of the moon and of the sun on the 

 tides was no sooner established, than it became eminently probable that 

 an influence exerted so strongly upon a fluid so heavy as water, could 

 not but have the lighter and all but imponderable fluid of air under its 

 grasp. I speak not of the influence attributed to the moon in the pop- 

 ular language and belief of nations ancient and modern, — of Western 

 Europe and of Central Asia, in respect to disease ; but of the direct 

 and measurable influence of the moon and of the sun in respect to the 

 air. It is now clear, as the result of the observations at St. Helena by 

 my friend Col. Sabine, that as on the waters, so on the atmosphere, 

 there is a corresponding influence exerted by the same causes. There 

 are tides in the air as in the sea ; the extent is of course determinable 

 only by the most careful observations with the most delicate instru- 

 ments ; since the minuteness of the effect, both in itself and in com- 

 parison with the disburbances which are occasioned in the equilibrium 

 of the atmosphere from other causes, must always present great diffi- 

 culty in the way of ascertaining the truth — and had, in fact, till Col. 

 Sabine's researches, prevented any decisive testimony of the fact being 

 obtained by direct observation. But the hourly observations of the ba- 

 rometer made for some years past at the Meteorological and Magneti- 

 cal Observatory at St. Helena, have now placed beyond a doubt the 

 existence of a lunar atmospheric tide. It appears that in each day the 

 barometer at St. Helena stands, on an average, four thousandths of an 

 inch higher at the two periods when the moon is on the meridian above 

 or below the pole, than when she is six hours distant from the merid- 

 ian on either side; the progression between the maximum and mini- 

 mum being moreover continuous and uninterrupted : — thus furnishing 

 a new element in the attainment of physical truth ; and, to quote the 

 expression of a distinguished foreigner now present, which he uttered 

 in my own house when the subject was mentioned, ' We are thus mak- 

 ing astronomical observations with the barometer' — that is, we are reas- 

 oning from the position of the mercury in a barometer, which we can 

 touch, as to the position of the heavenly bodies which, unseen by us, 

 are influencing its visible fall and rise. ' It is no exaggeration to say, 

 — and here I use the words of my friend, the Rev. Dr. Robinson,— 

 'that we could even, if our satellite were incapable of reflecting hg ht » 

 have determined its existence, nay, more, have approximated to its ec- 

 centricity and period.' 



u I am unwilling to quit this subject without expressing any deep 

 sense of the services rendered to science by the patient, laborious, un- 

 obtrusive observation and researches of my eminent friend, Col. Sabine* 

 in meteorology, and above all, magnetism, in connection with differen 

 and very distant points of the earth : researches undertaken, some o 

 them, before public attention was so generally called to the subject as 

 it has been in later years— (since the British Association urged the 

 importance of such investigation upon the government at home ;) an 

 undertaken at great sacrifice of domestic comfort, and at the risk o^ 

 life, not in the ordinary duties of his noble profession, but in the Pur- 

 suit of science for its own sake, — science one year at the North role* 

 and the next, I think, in Sierra Leone. The reputation thus acquire 

 does not come quickly, but it comes surely, and will survive perm* 



