178 Humboldt on Isothermal Lines, and the [March, 



the level of the ocean. The highest point in Europe where any 

 observations have been made, is the Hospice de St. Gothard, at 

 about 6,400 feet above the sea ; but in South America the town 

 of Quito is about 9,000 feet, Huancavelica about 11,670 feet, and 

 the mine of Santa Barbara as much as 14,400 feet above the sea, 

 or more than double that of St. Gothard. In order to compare 

 the residts which were obtained in the equinoxial regions with 

 the mean heat of temperate climates, it was necessary to find 

 out different situations, at intervals of 10° of latitude, but on 

 different meridians, the mean temperature of which had been 

 accurately ascertained. These will form so many fixed points, 

 through which the isothermal lines, or the lines of equal temper- 

 ature, may pass. In collecting facts for ascertaining these 

 stations, comparatively few of the numerous thermometrical 

 observations that have been published could be employed. Many 

 of the observations contradict each other ; in many cases we do 

 not know under what circumstances they were made; and we are 

 frequently obliged to reject such as, in other respects, appear 

 correct, because we are not acquainted with the absolute height 

 of the place at which they were made. This is remarkably the 

 case with almost the whole of Asia ; and it is not a little singular 

 that, while there are more than 500 stations in the equinoxial 

 district of America, many of them mere villages, or even hamlets, 

 the altitude of which has been exactly determined, we are igno- 

 rant of the height of Bagdat, Aleppo, Ispahan, Delhi, and many 

 other large and ancient cities in the Old World. In comparing 

 the temperatures of different places, it is, however, quite neces- 

 sary either that they should be upon the same level, or that a 

 proper allowance should be made for any difference which there 

 may be in this respect. 



In the old continent the only good observations which can be 

 employed to form our calculations are limited by the parallels 

 of 30° and 70° of latitude, and by the meridians of 30° east and 

 20° west longitude ; the extreme points of which are, the island 

 of Madeira, Cairo, and Cape North ; it comprises about \ the 

 circumference of the globe from east to west. There are many 

 circumstances connected with Europe, partly depending upon 

 its natural form and situation, and partly upon the state of its 

 civilization, which have given a peculiar character to its climate, 

 different from that of other regions in the same latitude. But as 

 this has been the abode of men of science, they have considered 

 the laws which regulate the temperature of that part of the 

 world as what are applicable to all the others. In this, however, 

 they have fallen into some considerable errors, the causes and 

 the amount of which we must endeavour to discover and appre- 

 ciate. It is not with the temperature of the atmosphere, and 

 with the magnetism of the globe, as with those phenomana 

 which are determined by a single cause, and may be considered 

 as distinct from all disturbing causes. From their nature, they 



