242 



A. G. Hoivard, — The 



[May 4, 



and the barometer oscillate violently. Inequalities of surface contour, 

 or patches of intensely heated soil will be enough to generate inde- 

 pendent cyclones, which, once formed, will roll along between the 

 two currents and pass away to the east. These little storms are 

 very annoying in upsetting all the pre-arrangements of the forecaster, 

 and very often make him look foolish before the world. 



I have observed the two opposing currents remain stationary for 

 a week over the Colony, and cyclone after cyclone roll along the 

 intervening area. 



On Fig. 3 I have embraced more of the two currents, and the 

 storm in the form of an isobaric chart. 



. (Fig- 3.) 



E is the equatorial current and D the polar one, A being the area 

 of low pressure at the plane of meeting, close to the surface of the 

 ground. It will be noticed that the winds flow off the areas of high 

 pressure D and E, first in straight lines on all sides, which by the 

 revolution of the earth are gradually deflected in a direction opposite 

 to the motion of the hands of a watch on its face. Were there no 

 disturbing element, these winds would become more and more 

 circular ; but coming under the influence of the area of low pressure, 

 they are drawn towards it from all sides. Those of the equatorial 

 current E are seen to blow straight in, and those from the polar one 

 D being deflected round the area in a direction similar to watch hands.. 



I will now refer to Fig. 1 again. 



All atmospheric currents as they travel along contain a certain 

 amount of moisture, although this may be in a state of invisibility. 

 It is a well-known fact that the temperature decreases as we ascend 

 into the atmosphere, and also that if atmosphere containing moisture 

 be carried to an altitude where the temperature is lower than the 

 dew point of its oi'iginal position, the moisture condenses, and clouds 

 form. 



