30 FACTS IN METEOROLOGY. 



cloud and rain, and two of clear weather occur. Some additional facts 

 relative to the same subject will claim attention in the present number. 



1. It might readily be expected that in a mass so changeable as the 

 atmosphere, these conditions should vary considerably at each recur- 

 rence. The circumstances of the cloud and rain, and of the clear weather 

 of one week do not exactly agree with those in the next. The degree 

 and duration of the cloudiness, and the quantity of the rain or snow of 

 Tuesday night of the present week will not agree exactly with those of 

 the past week ; there may be either less or more according to the quan- 

 tity of moisture in the air, the temperature of the day or two next pre- 

 ceding, and the currents at the same time. It may happen therefore that 

 any of these periods of rain may pass by with nothing more than a par- 

 tial obscuration of the sky, being followed at its next recurrence with 

 the usual accompaniment of rain. It sometimes happens too that the 

 cloud begins to cover the sky some hours or even a day before the regu- 

 lar time of its occurrence, but then it may be expected to continue just 

 about as much longer afterwards, shortening the time of clear weather, 

 and perhaps extending on to unite with the next period for cloud, so as 

 to obscure the sky for a whole week. Thus when the cloud and rain 

 of one period extend beyond 24 hours, they will most likely continue 

 as rain, drizzle or fog until the third day, and then break away, or unite 

 with that which is to follow. Hence we have damp and rainy weather, 

 sometimes for three days, sometimes for a whole week, and sometimes, 

 as in June, 1835, for a whole month, without affording a sight of sun, 

 moon, or stars. The reverse precisely sometimes takes place; the clear 

 weather extending over the whole week, and even longer. During the 

 occurrence of this state of things the winds are more gentle, and less 

 variable than ordinarily, and blow, during the clear weather, from some 

 part of the western half of the horizon. 



2. Nor is this succession of two changes in about seven days and a 

 half, or of one each three days and three-quarters, confined only to what 

 are termed settled rains, that is, to those rains which are not mere show- 

 ers, but which extend over several successive hours in duration, and a 

 wide ten-itory in extent. It extends also to the thunder showers of sum- 

 mer. These too, instead of being occasional, and interlopers as it were, 

 according to the prevailing impression, belong to the regular system of 

 rains. The electric display accompanying them is merely an accidental 

 circumstance resulting from the active local condensation of vapor, and 

 not always absent from the settled rain at its commencement or end. 

 Not unfrcquently do we lind the extended rain ushered in by thunder 

 clouds. Side by side, like the front ranks of an army in battle array. 



