4s Description of the Mounialn Barometer* 



of the earth, to a considerable precision, than any other 

 known process, that it might have been supposed that, in 

 the course of thirty years, which have elapsed since this 

 branch of science has been perfected, a very great number 

 of observations would have been made, and the heights of 

 almost the whole surface of our own country ascertained by 

 the numerous travellers who continually traverse it. The 

 contrary is however the case; and the small number of ob- 

 servations of this kind may be attributed to several causes. 



The instruments are of considerable expense, and, from 

 their complicated construction, easily liable to be out of 

 order in the course of a long journey. 



The observ^atifens themselves, though each not taking up 

 any very long time, yet, when multiplied on every hill and 

 valley, as they ought to be, for the purpose of obtaining a 

 just idea of the face of the country surveyed, in the aggre- 

 gate consume much of the traveller's time; and the consvtant 

 unpacking and re-packing the instrument, becomes a greater 

 labour than our natural indolence easily submits to. 



It has moreover been generally supposed, that two instru* 

 ments and two observers making simultaneous observations 

 at the upper and lower stations of the height to be measured, 

 are indispensably necessary. This, of course, would put it 

 out of the power of a solitary traveller to make any obser-5^ 

 v^tions at all. 



Whether from these, or other causes, the fact is, that 

 whoever reads the numerous Tours, Surveys, and Reports 

 of the different parts of our island, published within these 

 last twenty years, and many of them professedly with a view 

 to science, either of agriculture, mineralogy, or geology, 

 will be perpetually disappointed, by meeting with mere 

 guesses at the elevations of the tracts of country described : 

 though a knowledge of those elevations is almost indispen- 

 sable to the geologist, mineralogist, and military surveyor; , 

 highly iiseful to the scientific agrictdtiirist, and very inter- 

 esting to every one, who, from mere motives of enlarged 

 and enlightened curiosity, rends books of travels, or cm- 

 ploys his own leisure in traversing the countries described by 

 other voyagers. 



I cannot. 



