308 Astronomical and Nautical Collections. 
tor moderate; but at the latitude of about 42°, where the rotatory 
velocity of the earth’s surface is equal to the velocity with which 
any impression is transmitted by the atmosphere, or at about 40° 
of the lunar tide, the height of the oscillations will only be limited 
by the resistances, the greatest elevation occurring about three hours 
after the transit of the luminary; nearer the pole they will occur ear- 
lier than this, and nearer the equator a little later.” Possibly, in- 
deed, the slight obliquity in the direction of the high water might 
have some little tendency to equalize the height of the tides of dif- 
ferent parts of the atmosphere : ‘‘ it seems, however, to be a mis- 
take to suppose, that the effects of the atmospherical tides must be 
more perceptible near the equator than in temperate climates; and 
the variations of the barometer, which have been observed between 
the tropics, are manifestly independent of the lunar attraction, oc- 
curring regularly at certain hours of the day or night; as indeed — 
the tides of the ocean might have been expected to occur, if they had 
really been derived from the” meteorological causes to which some 
authors have ‘ chosen to attribute them.” 
Of the article Trpxs in the Supplement, the first. section relates 
to the ‘‘ Progress of contemporary tides as inferred from the times 
of high water in different ports.” The author’s conclusions from a 
tabular comparison of observations are these :— 
“ First, that the line of contemporary tides is seldom in the ex- 
act direction of the meridian, as it is supposed to be universally in 
the theory of Newton and of Laplace ; except, perhaps, the line of 
the twenty first hour [of Greenwich time] in the Indian ocean, 
which appears to extend from Socotora to the Almirantes, and the 
Isle of Bourbon, lying nearly in the same longitude. 
‘« Secondly, that the southern extremity of the line advances as it 
passes the Cape of Good Hope, so that it turns up towards the 
Atlantic, which it enters obliquely, so as to arrive, nearly at the 
same moment, at the Island of Ascension, and at the Island of 
Martin Vaz, or of the Trinity. 
“Thirdly, after several irregularities about the Cape Verd Islands, 
and in the West Indies, the line appears to run nearly east and 
west from St. Domingo to Cape Blanco, the tides proceeding due 
