the Heights of Ben-Lomond, 6fc. 127 



The mean of tliese two heights i»3175 feet, and they differ 

 only by 2 feet from each other, or only 1 foot from the mean. 

 This shows that, even at the distance of 60 miles, very consider- 

 able confidence may be placed in the determination of heights 

 by the barometer, when the observations are carefully made 

 with good instruments under favourable circumstances. It may 

 be remarked, however, that the barometer at Edinburgh stood 

 very steadily for some days previous and subsequent to the 

 time at which our observations were made ; and perhaps a like 

 degree of consistency, at such a distance, could not be expected, 

 if the barometer had been in a fluctuating state. 



It was intended to have determined the height geometrically, 

 at the same time, in order to judge of the degree of accuracy, of 

 our formula and tables ; but the unsteady state of the weather, 

 during the early part of the month of August, prevented the 

 attempt. On this account we shall content ourselves, for the 

 present, by comparing it with the height computed from data, 

 communicated by Colonel Colby to Professor Leslie, and given 

 in the copious and valuable potes appended to his Elements of 

 Geometry, fourth edition, page 434. 



Height geometrically by Professor Leslie, - 3177 feet 

 Mean of our two barometrically, - 3175 



Difference only, - - 2 feet. 



On account of this close coincidence, it is probable both ^re 

 very near the truth. 



As an appendix to this paper, may be added a determination 

 of the quantity of water annually discharged by the river Leven 

 from the basin of Loch-Lomond. 



Having spent a day or two at Kirkland, near Bonhill, with a 

 few acquaintances, I was induced, from the opportunities which 

 I then enjoyed, to attempt this problem. In it I was cordially 

 assisted by my friend Mr Robert Davie, who was residing there 

 at the time, in taking the necessary measurements. By these I 

 found the discharge to be about 59,939 cubic feet per minute. 

 Now as 36 cubic feet of fresh water is very nearly equal to a 

 ton, this gives 1665 tons per minute ; and, supposing the year to 

 consist of 365 days 5 hours 49 minutes, the annual discharge, 

 at that rate, will be 877,925,085 tons. But as the river was 



