OP ARTS AND SCIENCES. 33 



the afternoon of this day, several tornadoes occurred in eastern 

 Pennsylvania. 



Aug. 4. The low pressure centre passed slowly along north of the 

 St. Lawrence, and gave rain that began gently on the afternoon of the 

 3d, and continued through the night, becoming very heavy, with strong 

 south or southeast wind, just before clearing in the morning, and this 

 latter part of the rain was accompanied with violent thunder and light- 

 ning, striking in several places. Many observers speak of this storm 

 as a peculiar one, describing it as an ordinary southeast storm during 

 the night, but culminating in a violent thunder-storm with torrents of 

 rain as it was about to break away. The time of rain beginning can- 

 not be used in this case as a guide to the progress of the storm ; but 

 the hour of loudest thunder and heaviest rain serves well instead. This 

 shows the storm to have passed over western Connecticut and Massa- 

 chusetts and southern Vermont shortly after midnight, reaching the 

 Connecticut valley at 2'', Rhode Island to the upper Merrimack valley 

 between 8'^ and 9^, Boston about 9^.30, Salem and Newburyport at 

 lO'^, Cape Ann at 10^30, Provincetown at ll'', and appearing later on 

 the Maine coast. This gives an east-northeast progression of ten or 

 twelve miles an hour. The storm may have increased in intensity 

 from central Massachusetts, where several good observers made no 

 report, to the eastern part of the State, where reports are numerous, 

 and where many stations measured two or three inches of rain. The 

 wind was not noticeably affected by the rain ; it was strong south- 

 east, with heavier gusts during the storm, and soon fell off to gentle 

 southwest as the sky cleared. The temperature was rising in eastern 

 Massachusetts before the heavy rain, and fell five or ten degrees dur- 

 ing its continuance. As the storm passed away, the temperature rose 

 rapidly, and the mean maximum of the day was 84°. This storm was 

 therefore quite unusual in separating a period of cooler from a period 

 of warmer weather. 



A second storm was felt in Vermont in the late afternoon and even- 

 ing, possibly derived from an afternoon storm in New York State ; its 

 lightning was seen in eastern Massachusetts. Many observers also 

 report heat-lightning in the southeast at 20*^ to 22^ but we have no 

 direct record of the storm from which it came except that the observer 

 at Provincetown saw a bank of low clouds out over the ocean at these 

 hours, with frequent and brilliant flashes of lightning. 



Aug. 5. A warm day, with southwest winds drawn towards the 

 low pressure centre, now north of the Gulf of St. Lawrence. A 

 thunder-storm came down the Mohawk valley shoi'tly after noon, 



VOL. XXII. (n. 8. XIV.) 3 



