OF ARTS AND SCIENCES. 45 



storm-front, so that a graphic average is obtained of the distribution of 

 these elements in the whole storm. An hour and a half or an hour 

 before the storm, clouds are seen rising on the western horizon, while 

 the winds are light southerly, and the temperatures high (85-95°). 

 Nearer the storm-front, the clouds are seen to rise higher, and the tem- 

 perature falls slightly, but the wind does not change significantly. The 

 first thunder is heard from thirty to sixty minutes, and the clouds are • 

 recorded as reaching the zenith or passing overhead from ten to thirty 

 minutes, before the rain. The sudden change from gentle southerly 

 wind to the northwest squall seldom comes more than fifteen minutes 

 before the rain, and is generally only five to seven minutes before it ; 

 with this change the temperature falls rapidly. The squall seldom 

 continues after the rain begins. The heaviest rain is marked close to 

 the rain beginning in many cases ; in others, it fsills from seven to 

 twenty-five minutes later. The loudest thunder runs from ten to 

 thirty-five minutes after the rain-front, and the lightning strokes, as far 

 as reported, fall with one exception between thirteen and twenty-seven 

 minutes after the rain-front. Already at twenty to twenty-five minutes 

 after the rain had begun, the western horizon is seen lighting up, 

 and soon the clouds begin breaking away ; their rear edge is overhead 

 iji an hour to an hour and a half, while the rain had ceased fifteen 

 minutes sooner on the average, its shortest duration being thirty, and 

 longest ninety minutes. During the rain, the temperature stood fifteen 

 to twenty-five degrees lower than before the storm, and the winds were 

 light and variable ; as the storm passed over in the afternoon, an abso- 

 lute rise of temperature after its passage is seldom seen, and then is 

 faint ; but a relative rise is clearly found in the maintenance of an 

 almost uniform temperature past those hours when it ordinarily de- 

 creases most rapidly. Rainbows make their appearance between an 

 hour and an hour and a half after the rain beginning, and the last 

 thunder is heard from one to two hours after the storm began. We 

 gain easily, from such a portrait as this, a general view of the storm 

 that can be acquired only with much labor in other ways. As to the 

 accuracy of the view, that can be greatly increased as our observers 

 come to use more uniform methods in making their records. 



Storms of July 2\. — The thunder-squall that traversed southern 

 New England on the morning of July 21 was in some respects the 

 most interesting storm of the summer. The persistent maintenance of 

 its several features throughout its whole path is especially instruct- 

 ive. It closely resembles squalls that have been described in Iowa by 

 Hinrichs. 



