E. Loomis — Cohtrihnthms to Mtroi'ohxjlJ. 11 



haps of a few cases, in most of which the storm extended 

 beyond the stations of observation, and adequate information 

 respecting it has not been obtained. As the limits of this arti- 

 cle will not allow me to take up each case in detail, I shall 

 confine my notice to those cases which were most remarkable 

 either for a very great velocity of progress, or a very small 

 velocity. There are fourteen cases in which the low center 

 advanced at a rate exceeding fortv miles per hour, viz: Xos. 4. 

 13, 25, 36, 41, 44, 46, 48, 49, 50, 51, 53, 66 and 67. In Nos. 4, 

 13, 66 and 67 there was a trough of low pressure extending 

 more than one thousand miles across the United States from 

 southwest to northeast. A considerable fall of rain on the 

 front side of the principal center of low pressure carried the 

 low center forward with unusual velocity, although the change 

 of pressure in eight hours was small. In Nos. 66 and 67 there 

 was an area of high pressure on the northeast side and an- 

 other on the northwest side, which condition seems to favor the 

 rapid progress of low centers as shown in mv twelfth paper. 

 In No. 25 the conditions were very similar to those represented 

 on Plate IV accompanying mv twelfth paper, viz: a full of rain 

 and snow of great geographical extent on the northern side of 

 the low center, associated with an area of high pressure on the 

 northeast side and another on the northwest side. In Nos. 36 

 and 41 the lowest isobar formed a very elongated oval, whose 

 longest diameter extended from southwest to northeast. The 

 principal rain -fall reported was on the south side of the prin- 

 cipal low center, but. since the lowest isobar extended north- 

 ward bevond the stations of observation, it is not known what 

 the rain fall was on the northern side. These two cases were 

 therefore apparently similar to Nos. 4, 13, 66 and 67. More- 

 over in No. 36 there was an area of high barometer on the 

 side and another on the northwest side. In Nos. 44, 

 46 and 48 the low center, which was already near the Atlantic 

 coast, moved rapidly eastward, being appare itl\ inil n nerd by 

 the great rain-fall near the coast. Many cases have been found 

 in which a storm moving eastward from the United States to 

 the Atlantic Ocean, has suddenly acquired a great increase of 

 intensity, attended by a great fall of rain or snow. Nos. 44, 

 48 and is were apparently of this class. In Nos. 49 and 50 the 

 low center was near the Atlantic coast, and adhered closely to 

 the coast line, being preceded by a heavy fall of snow. Also 

 in No. 46 there was an area of high barometer on the northeast 

 side and another on the northwest side. In No. 51 there was 

 also an area of high pressure on the northeast side and another 

 on the northwest side, with heavy rain on the east side of the 

 low center. Also the winds which attended the area of high 

 pressure on the northwest were unusually violent, being forty- 



