158 PHILOSOPHY OF STORMS. 



sun sinks below the horizon, and also the time when his 

 last rays fall on the top .of the cloud ; at the same moment 

 take the angular height of the top of the cloud with your 

 sextant, and also its direction ; then you will have data for 

 finding the height of the cloud by trigonometry : or the dis- 

 tance of the cloud may be computed by observing the inter- 

 val of time between a flash of lightning emanating from it, 

 and the succeeding thunder. This interval in seconds mul- 

 tiplied by 1142, will give the distance of the cloud in feet. 

 The distance and angular elevation being known, the height 

 can be ascertained by a simple trigonometrical calculation. 

 One was so calculated by the writer of this circular, and 

 found to be about ten miles high. (81.) Further observa- 

 tions on this point are desirable. 1 



128. Sir John Herschel has recommended that hourly 

 observations, for thirty-seven successive hours, be made four 

 times a year, beginning at six, A. M., on the 21st of March, 

 the 21st of June, the 21st of September, and the 21st of 

 December. Many observers, in various parts of the world, 

 have commenced these observations, and some important 

 facts have already been discovered by them. We hope that 

 very many of our correspondents will follow the example ; 

 and to those who do, we recommend, according to a sugges- 

 tion of Mr. Redfield, that some account of the weather, before 

 and after this period, be given especially if a storm oc- 

 curs, that all the phenomena of the storm may be known. 



At the time of all storms, it will be highly important to 

 make the observations as numerous as convenient, always 

 noting the exact time of taking the observation, even to a 

 minute. In this way, so many almost simultaneous obser- 

 vations will be made on the same storm, that even a sum- 

 mer's thunder shower cannot spring up in our borders with- 



1 As the dew point in this country in the summer, is much higher than it 

 is in Great Britain, it ought to be expected that clouds would shoot their tops 

 much higher here than there ; because the steam power is greater. 



