26 VEGETABLE SUBSTANCES. 



and at a much lower level than Xalapa, that grain 

 comes to full perfection. Humboldt offers, as reasons 

 for this variance from the usual rule, the exposed 

 situation of the district, and the prevalence of cool 

 winds, which serve to modify the otherwise unfavoura- 

 ble influence of the climate. ' I have seen,' says this 

 observant traveller, ' in the province of Caraccas, the 

 finest harvests of wheat near Victoria, (latitude 10 

 13') at 500 or 600 metres (1640 or 1968 feet) of 

 absolute elevation ; and it appears that the wheaten 

 fields which surround the Quatro Villas, in the island 

 of Cuba (latitude 21 58'), have still a smaller eleva- 

 tion. At the Isle of France (latitude 20 10') wheat 

 is cultivated on a soil almost level with the ocean.'* 



Circumstances altogether unconnected with climate 

 must be taken into account in determining the relative 

 agricultural capabilities of Mexico, where the absolute 

 absence of rain, throughout a large portion of the 

 time when the plant is on the ground, must be, in a 

 high degree, detrimental to wheat husbandry, unless 

 artificial means were resorted to, as in Nubia, for 

 supplying the natural deficiency of moisture. 

 Throughout a great part of the temperate regions of 

 New Spain the farmers are compelled to adopt the 

 system of artificial irrigation. This is effected by the 

 agency of canals and reservoirs, which are supplied 

 from the rivers, and which are so constructed that the 

 water may be dispensed at pleasure over any and 

 every part of the farms. 



In districts where the system of artificial watering 

 is fully adopted, the fertility of the Mexican farms is 

 extraordinary, far beyond anything experienced in 

 the richest soils of Europe, the wheat harvest being 

 commonly thirty-five and forty for one, and some 

 considerable estates yielding even fifty and sixty 



* Humboldt's New Spain, p. 454. 



