OF AETS AND SCIENCES. 27 



July 6. The western centre of low pressure on this day followed 

 a curious retrograde course from Lake Superior towards Lake Winni- 

 peg. Under its influence, New England had warm southerly winds, 

 turning to southeast or east along the eastern coast, and southwest 

 inland. Several local showers of no great intensity arose in Vermont, 

 New Hampshire, and Eastern Massachusetts in the afternoon and 

 evening, moving east-northeast at a moderate rate ; they appeared to 

 be developed from ordinary cumulus clouds, whose motion was per- 

 sistent from the southwest or south, little affected by the inflection 

 of the surface winds along the coast. As an example, a shower that 

 passed over the south shore of Boston Bay may be mentioned. The 

 morning sky had been nearly covered with light cirro-cumuli, beneath 

 which large cumuli formed rapidly about noon, and united into a long 

 nimbus stretching about north and south, and moving to the north- 

 east : the light surface winds at one station were east before the rain, 

 calm during the light shower, west for a short time after the shower, 

 and then east again through a fair afternoon. Other stations report 

 a continued east or southeast wind during and after the passage of the 

 shower. The showers in New Hampshire were heavier: in the east- 

 ern part of the State they also presented the peculiarity of advancing 

 from the southwest over an easterly wind. 



July 7. A few local showers, with moderate electric action. The 

 winds were still warm southerly, under the influence of high pressure 

 off the coast and the low pressure centre that hesitated over Lake 

 Winnipeg. 



July 8. A new centre of low pressure appears on the morning 

 weather map for this date in Dakota. Violent thunder-storms appeared 

 south of the Great Lakes, but none formed in New England, although 

 the temperature rose rapidly (mean max. of 7th, 80°; of 8th, 87°). 



July 9. The newly formed area of low pressure moved eastward, 

 north of the lower lakes, and on the afternoon of this day stood near 

 Quebec. Under its influence the mean maximum temperature rose 

 to 91°, and the largest storm of the summer was developed, extending 

 with almost continuous front from southwestern! to northeastern New 

 England, and accompanied by all the characteristics of a full-grown 

 storm. It forms the subject of a special description on ]). 38. 



July 10. The low pressure centre of the previous day turned 

 southward from the St. Lawrence valley, and this morning stood in 

 western Maine. Had this attitude been preserved through the hotter 

 hours of the day, we should doubtless have had more than scattered 

 reports of light thunder-showers and heat-lightning; but it moved 

 away eastward, leaving an area of cool fine weather behind it. 



