157 



Mr. Johnstone, measuring a base by means of the log, 

 found the height of the Peak to be 2023 toises*. Mr. de 

 Churruca in a voyage to the Straits of Magellan, made in 

 1788, attempted also to determine the height of the volcano, 

 by a geometrical operation while under sail f. He found it 

 2193 toises, " congratulating himself on having attained a 

 greater exactness than could reasonably have been expected 

 (toda esperanza rational) , since the barometrical heights calcu- 

 lated by Bezout X gave the same number of toises." It is 

 the same with the measurement of mountains, as with the 

 determinations of latitudes and longitudes. The observers 

 are satisfied with their operations, when they find them agree 

 with some old results, to which they give the preference 

 above all others. 



Mr. Cordier measured the Peak on the 16th of April, 

 1803, employing Mossy 's barometer, which he had boiled 

 the preceding evening, and in very fine and settled weather, 

 which lasted a month. " The instruments were placed to 

 the windward of the Peak, and the barometric height was 

 brought to the temperature of the ambient air. The corres- 

 pondent barometer, of English construction, differed only 

 -1 of a line, ancient French measure, from that of Mossy 

 employed by the traveller. Though the persons appointed 

 to make the observations at Orotava, Messrs. Little and 

 Legros, did not employ the nonius, they estimated never- 

 theless the heights of the mercury with great exactness to 

 fourths or fifths of a line §/' Mr. Cordier took account 



P£rouse's voyage (t. ii, p. L8) should have expressed so many 

 doubts of the results obtained by the barometer. 



* Lord Macartney's Voyage, t. 1. p. 158. 



f Viage al Magellanes, Apendice, p. 10. 



% Cours de Mathematiques, vol. iv, p. 416 (edit, de 1775). 

 § These particulars and barometrical heights, which were 

 not printed in the Journal de Physique, t. lvii, p. 60, have 



