1883.] On a Series of Barometrical Disturbances. 149 



The mean between the two values obtained from the waves travel- 

 ling against the earth's motion of revolntion and those travelling with 

 it is 2 h. 24 m. Greenwich mean time, or 9 h. 24 m. local time, 

 27th August. 



The velocity of the waves in miles will be for those which travel 

 from east to west 674 miles per hour, and for those passing from west 

 to east 706 miles per hour. The velocity of sound is for a temperature 

 of 50° F. 757 miles an hour, and for 80° F. 781 miles an hour. With 

 a temperature as low as zero F. the velocity will only be reduced to 

 723 miles an hour, which is still considerably in excess of the greater 

 of the observed velocities. The excess of the velocity of the waves 

 which travelled in the same direction as the earth's motion of revo- 

 lution, that is, from west to east, over that of those which passed in 

 the opposite direction, is about 32 miles an hour, which might be 

 accounted for by the circumstance that the winds along the paths of 

 the waves would, on the whole, be from the west, which would cause 

 an increase in the velocity of the one set, and a diminution in that of 

 the other, so that the observed difference of 32 miles would correspond 

 to an average westerly wind of 16 miles an hour, which is not im- 

 probable. 



It should be observed that the path of the wave which passed 

 Toronto approached very near to the North and South Poles, and that 

 the velocity in both directions appears to be somewhat less than in 

 the waves which passed over central Europe. The wave which passed 

 northwards over Asia travelled at the rate of about 660 miles an 

 hour, or about 15 miles an hour slower than the wave which passed 

 over Great Britain from east to west. This reduction of velocity 

 seems to be within the limits of what might be due to the low tem- 

 perature of the regions. 



The wave travelling from east to west having been perceptible on 

 the barometer traces at several of the stations until about 122 hours 

 after its origin, and its velocity having been 674 miles an hour, it had 

 travelled before its extinction more than 82,200 miles, and had passed 

 3^ times round the entire circuit of the earth. 



It is further worthy of notice that during the 30th and 31st of 

 August and 1st September, a very severe cyclonic storm was crossing 

 the North Atlantic, and that the wave coming from the westward 

 early on the 31st, No. YI of the series, must have passed on in front of 

 the cyclone, and that its next transit would have carried it into the 

 very centre of the cyclone near the British Isles on the afternoon of 

 the 1st September. This perhaps accounts for no trace of it being' 

 found, though the wave coming from the eastward on the morning of 

 that day, just before the cyclone had arrived, No. VII, was discernible. 



There is no definite statement, so far as I am informed at present, 

 of the true time of any particularly severe shock or explosion at 



