CONCLUSIONS ON ANCIENT CLIMATES. 17 



We may also be misled bj our ignorance of the commercial re- 

 lations existing between pnvage tribes. Extremely rude nations, 

 in spite of their jealousies and their perpetual wars, sometimes 

 contrive to exchange the products of provinces very widely sepa- 

 rated from each other. The mounds of Ohio contain pearls, 

 thousfht to be marine, which must have come from the Gulf of 

 Mexico, or perhaps even from California, and the knives and 

 pipes found in the same graves are often formed of far-fetched 

 material, that was naturally paid for by some home product ex- 

 ported to the locality whence the material was derived. The art 

 of preserving fish, flesh and fowl by drying and smoking is widely 

 diffused and of great antiquity. The Indians of Long Island 

 Sound are said to have carried on a trade in dried shell-fish with 

 tribes residing very far inland. From the earhest ages, the in- 

 habitants of the Faroe and Orkney Islands, and of the opposite 

 mainland coasts, have smoked wild fowl and other flesh. Hence 

 it is possible that the animal and the vegetable food, the remains 

 of which are found in the ancient deposits I am speaking of, may 

 sometimes have been brought from chmates remote from that 

 where it was consumed. 



The most important, as well as the most trustworthy, conclu- 

 sions with respect to the climate of ancient Europe and Asia, are 

 those drawn from the accounts given by the classical writers of 

 the growth of cultivated plants ; but these are by no means free 

 from uncertainty, because we can seldom be sure of an identity 

 of species, almost never of an identity of race or variety, between 

 vegetables known to the agriculturists of Greece and Rome and 

 those of modern times which are thought most nearly to resemble 

 them. Besides this, there is always room for doubt whether the 

 habits of plants long grown in different countries may not have 

 been so changed by domestication or by natural selection, that the 

 conditions of temperature and humicHty which they required 

 twenty centuries ago were different from those at present de- 

 manded for their advantageous cultivation.* 



plorations and Surveys for Pacific Railroad, vol. ii., 1855, Lieut. Beck'svith'8 

 Report, p. 43. See also American Naturalist for May, 1870, and especially 

 Stevens, Flint Chips, London, 1870, pp. 77 et seq. 



Mariette Bey lately saw an Egyptian barber shave the head of an Arab with 

 a flint razor. 



* Probably no cultivated vegetable affords so good an opportunity of study- 



