84 Questions Jbr Solution relating to Meteorology/, 



Although this table is incomplete, and founded on observa- 

 tions of only five years'* continuance, and although the north and 

 north-east winds are entirely omitted, there results from it no 

 less important a consequence than this, — that if the direction of 

 the winds exercise, at Marseilles, any influence on barometrical 

 heights, that influence is very slight, and ought not always, in 

 the case of winds of similar denominations, to have the same 

 sign as in the north of France. Thus, while at Paris the south- 

 west wind depresses the barometer considerably below the mean, 

 its influence at Marseilles is positive ; on the other hand, the 

 north-west wind, which causes a considerable rise in the baro- 

 meter at Paris, is that which produces the lowest depression at 

 Marseilles, 



When observations such as these have been made at many 

 different places, they will probably put meteorologists in a con- 

 dition to explain a phenomenon which has hitherto baffled all 

 their efforts. 



Of the Diurnal Variations of the Barometer. — Numerous me- 

 moirs have been published on the diurnal variation of the baro- 

 meter. This phenomenon has been studied from the equator 

 to the regions in the vicinity of the pole, at the level of the sea, 

 on the immense plateaus of America, on the insulated summits 

 of the highest mountains, and the cause has notwithstanding re- 

 mained in obscurity. It is still necessary, therefore, to multiply 

 observations on the subject. In our climates, the vicinity of the 

 sea appears to manifest itself by a sensible diminution in the ex- 

 tent of the diurnal oscillation ; Does the same thing take place 

 between the tropics ? 



Observations on Rain. — Navigators occasionally speak of rains 

 winch fall on their vessels while traversing the equinoctial regions, 

 in terras which lead us to suppose that it rains much more abun- 

 dantly at sea than on land. But this subject still remains in the 

 domain of mere conjecture ; seldom has the trouble been taken to 

 procure exact measurements. These measurements, however, 

 are by no means difficult. Captain Tuckey, for example, made 

 many during his unfortunate expedition to the River Zaire or 

 Congo. We know that the Bonite will be provided with a small 



