M. Dove on the Wind. 205 



the cold frame in the spring of 1846, formed the plant which 

 flowei'ed in October, from which the description has been taken. 

 Some still maintain that the plant requires a stos'e-heat to make it 

 flower. In the Botanical Register for September 1847, the fol- 

 lowing remarks are made in regard to it : — " In cultivation this 

 should be regarded as a stove herbaceous climber, which grows 

 freely in a mixture of sandy loam and leaf mould in equal por- 

 tions." In the Botanic Garden of Edinburgh, the plant con- 

 tinues to thrive in a cold frame, as already mentioned. 



Memoir on the Changes in the mean direction of the Wind, in 

 the Annual Period, in North America. By M. DoVE. 



As there is no point on the surface of the earth where the 

 atmospheric pressure increases or diminishes without inter- 

 ruption, we must suppose that, as within the tropics, the 

 quantities of air which move below, towards tlie equator, con- 

 sist of a current running in a contrary direction to that above; 

 just as two currents wliich advance by the side of each other, 

 in the temperate zone, form an equilibrium, in such a manner 

 that the one which, in the space of a year, moves towards 

 the pole on certain points of a parallel, returns in an opposite 

 direction to the equator on other points of the same parallel. 

 At the same time, as the air which moves from the equator 

 towards this parallel, arrives at it with a higher temperature 

 which it gradually leaves in the ground over which it passes 

 in its progress towards the pole, a temperature which it does 

 not restore to the parallel on its return from the pole to the 

 equator, because cold air occupies a smaller space than warm 

 air ; it thence follows, that the polar current must be weaker 

 than the equatorial current. If the movement in the one di- 

 rection or the other has taken place in variable strata, it is 

 thereby rendered probable, that a place exists in the polar 

 current weaker than that in the equatorial current, and, con- 

 sequently, that the mean direction of the wind, from tliis 

 cause alone, ought to be equatorial throughout the whole 

 temperate zone. Besides, as the quantity which returns to 

 the equator is less, because the elastic accompaniments on 

 the air or steam is more and more condensed in its progress 

 to the pole, the returning air is deprived of an elastic element 



