40 Questiotisjbr Solution relating to Meteorology, 



which they are provided, to determine the dimensions of all the 

 halos tlmt appear to be elliptical. They will themselves perceive 

 that the inner edge of the halo, the only one which is distinctly 

 defined, is much better adapted for observation than the outer 

 edge ; but it is necessary, with regard to the sun, not to neglect 

 to indicate whether they have taken the centre or the edge as 

 the term of comparison. We likewise regard it as indispensable, 

 that the two rays diametrically opposite should be measured in 

 each direction, for certain observers have mentioned circular 

 halos, in which, if they are to be believed, the sun did not oc- 

 cupy the centre of the curve. 



Trade-Winds. — Perhaps it will excite surprise to see the trade- 

 winds announced as still affording a subject of important inves- 

 tigation ; but it must be remarked, that the practice of naviga- 

 tors has often confined them to simple notices, with which science 

 cannot be satisfied. Thus it is not true, whatever may have been 

 alleged, that to the north of the equator these winds constantly 

 blow from the north-east ; and that to the south of it they blow 

 uniformly from the soutJi-east. The phenomena are not the 

 same in the two hemispheres. In each place, moreover, they 

 change with the seasons. Daily observations of the real direc- 

 tion, and as far as practicable of the force of the eastern winds 

 which prevail in equatorial regions, would therefore be a useful 

 acquisition to meteorology. 



The vicinity of continents, on the western sides especially, mo- 

 difies the trade-winds in their strength and direction. It some- 

 times even happens that they are replaced by a west wind. 

 Wherever this change of the wind occurs, it is desirable to note 

 the time, the bearing of the neighbouring country, its distance, 

 and its general aspect. In order to shew the utility of this last 

 recommendation, it is enough to say, that a sandy country, for 

 example, will have a much speedier and more active influence, 

 than one covered with forests or any other kind of vegetation. 



The sea which washes the western side of Mexico, from Pa- 

 nama to the peninsula of California, between 8° and S2° north 

 latitude, will afford an opportunity to the officers of the Bonite 

 of observing a complete inversion of the trade- winds. They will 

 find, as we are informed by Captain Basil Hall, a nearly per- 

 manent west wind, in a situation when the east wind of the equi- 



