ADDRESS. 
xxxiii 
times t!ie mean anomaly of Venus increases at very nearly the same rate as 
thirteen times the mean anomaly of the Earth : its coefficient is 23" and its 
period 239 years. The combination of these two explains almost perfectly 
the error of epoch, winch had so long been a subject of difficulty. The 
discovery of these two inequalities, whether we regard the peculiarity of 
their laws, the labour expended upon the investigations, or the perfect suc¬ 
cess of their results, must be regarded as the most important stop made in 
physical astronomy for many years.” 
The doctrine of the influence of the moon and of the sun uu the tides w.a8 
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 ilu- 
lighter and all but imponderable fluid of air under its grasp. I «{>eak not of 
the influence attributed to the moon in the popular language and belief nf 
nations ancient and modern—of Western Europe and of Central in re¬ 
spect to disease; but of the direct and measurable influence of the attractions 
of the moon and of the sun upon (he air. It is tmw clear, as the result of the 
observations at St. Helenn by niy friend Col. Sabine, that, a» on the rvaters, 
80 on the atmosphere, there is a corresponding influence exerted by the same 
causes. 'I’here are tides in the air as in the seti; the extent is of course de¬ 
terminable only by the most careful observations with the most delicate in¬ 
struments; since the miDUteness of the eflbet, Loth In itself .nnd in compari¬ 
son with die disturbances which are occasioned in the equilibrium of the at¬ 
mosphere from other causes, must always present great difficulty in the way 
of ascertaining the truth—and Imd, indeed, till Col. Sabine’s researches, pre¬ 
vented any decisive testimony of the fact being obtained by direct observa¬ 
tion. But the liourly observauoiis of the barometer made Ibr some years past 
at the Meteorological and Magnctical Observatory at St. Helena, have now 
placed beyond a doubt the existence of a lunar atmospheric tide, ft appears 
tiiat in each day the barometer at St. Helena stands, on an average, Ibur- 
thousandtlis of an inch liiglier at the two periods when the moon is on the 
meridian above or below the pole, thnn when she is six hour.i distant from 
the meridian on either side; the progression between this inuximum and 
minimum being moreover ermtlnuoua and uninterrupted; tliu*. furnishing a 
new element ill the attainment of physical truth ; and, to quote the expres¬ 
sion oj a distinguished foreigner* now present, which lie uttered in my own 
house when the subject was raeniJoned, “ We .nre thus making .-istronomical 
ot)servaiion8 with the barometerthat is, we are reasoning 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 liill and rise. 
1 18 no exaggeration to say.”— and here I use the words of my friend, the 
f ev. Dr. Kobinsoii,— that we could even, if our satellite were incapable of 
reflecting light, have determined its existence, nay, more, have approximated 
to Us pxcctilriciiy and period." 
Amongst the pluenomena which the magnetic state of our globe presents, 
there are none perhaps which, when their laws should be correctly known, 
appeared more likely to show some physical connection which should con¬ 
duct to their physical causes, than the class of pheenomena kuown by the 
name of the “ periodical variations of the magnetic elements.” Of these, 
tlie earliest known were the changes in direction which a magnet soBjicnded 
horizontally undergoe-s at different hours of the day; and which had l>een 
ascertained to differ widely both in amount and in the hours of their occur¬ 
rence in different parts of the earth. To extend and systematise a know- 
* Ffofessor Laogberg, of Christiania. 
