OP ARTS AND SCIENCES. 41 



at 17.35, in torrents at 17.40. Beverly Farms, Mass.: S. W. breeze 

 and small black cloud in W. at 15.00 ; cloud grew till it extended 

 along W. and N. horizon ; at 1 7.00 thunder-clouds moved rapidly 

 towards S. E. ; at 17.10, edge of cloud in zenith, wind suddenly lulled, 

 but a furious W. squall came up at 17.15 ; rain began at 17.35, and 

 from 17.45 to 18.00 the rain poured in torrents. Quincy, Mass. : 

 Clouds first seen in N. W. at 15.35 ; high N. W. wind at 17.32 ; rain at 

 17.49. Bar Harbor, Me.: Dark cloud in N. W. at 15.30; clouds 

 darker and a heavy squall at IG.OO; heaviest wind at 17.30; rain 

 began 17.50. N, Attleborough, Mass. : Thunder-caps just visible over 

 N. W. horizon at 14.30; "edge of cloud overhead " at 16.55; rain 

 began at 17.55. Taunton, Mass. : A stratum of hazy clouds in N. W. 

 at 13.00; rising higher at 14.00; a lower stratum appears at 15.00; 

 rain at 18.05. S. Weymouth, Mass. : Clouds rising in N. W. and 

 thunder heard from them at 16.15 ; rain at 18.15. N. Marshfield, 

 Mass.: Heavy clouds in N. W. at 16.45; rain at 18.15. 



It appears from this summary that the cirrus overflow was often 

 seen two or three hours before the rain began ; its edge passed the 

 observer's zenith from an hour to an hour and a half ahead of the 

 j-ain, and therefore probably extended thirty to fifty miles in advance 

 of the main mass of the storm cumulus. The thunder-clouds them- 

 selves were often visible an hour or more before the rain fell. The 

 edge of the heavy cloud generally passed the observer's zenith three 

 to twelve minutes before, that is, two to six miles ahead of, the rain- 

 front; at several southeastern stations, where the storm's intensity 

 (and velocity ?) had decreased, this interval was over half an hour. 

 At one station (Oilman ton, N. H.) the rain began fifteen minutes 

 before the edge of the cloud passed overhead ; and this was, as the 

 observer well remarks, the more surprising, as no high wind occurred 

 with the storm there. 



The occurrence of " pocky " or " festoon " clouds (smooth masses 

 hanging from the under surface of broad cirro-stratus, convex down- 

 wards, like inverted cumulus clouds) is indicated by the following: 

 " Rockland, Mass. : The setting sun was shining upon the under re- 

 treating edge of the storm-cloud and showing all the irregularities of 

 its usually smooth under surface, — a very pleasing sight." These 

 clouds are of relatively rare occurrence ; they seem to be formed most 

 commonly in connection with thunder-storms, and they should be 

 carefully noted. The squall cloud is described in the account of the 

 wind. ' 



