316 Mr Galbraith's Barometric Measurements of Heights. 



therefore, to a naval country like Britain, whose pre-eminence 

 on the sea is quite essential to its existence, cannot for a moment 

 be disputed: — certainly its fleets should comprise in their 

 equipments all the advantages which science can obtain for 

 them. 



41. Although this subject has not been fully appreciated by 

 many persons, under an impression that the chances of damage 

 from lightning are too few and inconsiderable, even to warrant 

 the little trouble and expense necessary to avoid them, yet on 

 a careful examination of the logs of His Majesty's ships for a 

 few years only, it will be seen that such opinions are by no 

 means founded on reflection, and a judicious application of 

 lightning protectors on shipboard, is not only desirable for ship- 

 ping generally, but that in many cases it is absolutely essential 

 to their preservation. 



On the Measurement of the Height of Carnethy, one of the 

 Pentlancl Range of Hills, in the vicinity of Edinburgh, and of 

 the Peake ofTeneriffe. By Mr William Galbraith, M. A. 



Since my last communication on the measurement of heights 

 by the barometer, I have reconsidered the whole, and have 

 given here a more accurate investigation of the formula of 

 which I had then chiefly indicated the general principles, in or- 

 der to deduce an approximate rule that might be readily ap- 

 plied, easily recollected, and sufficiently accurate for moderate 

 heights. Indeed, it might be employed for any heights, if ob- 

 servations were made at intermediate points ; or by subdivid- 

 ing the observations, as has been suggested by Professor Leslie 

 in a neat practical rule which he has given in the notes append- 

 ed to his Elements of Geometry. This method, however, by 

 the additional observations or computations required to be 

 made, would give more trouble than the introduction of one or 

 two more terms of the series which will presently be given ; and 

 to make observations at intermediate points, might, from cir- 

 cumstances, be sometimes impracticable. As the shifting of the 

 decimalpoint and multiplication by the length of the mercurial 

 column, to obtain the necessary reduction of the mercury in the 

 upper barometer to the same temperature as that of the lower, 



