266 Observations on Humboldt^s Works 



toises * = 4 : 3 ; for the distribution of latitude 80" : 71° t = 

 10 : 9. If the proportions were the same, all vegetation of 

 trees must cease at 60° of latitude. 



Corn ascends, according to M. Humboldt, at the equator to 

 the height of i,600 toises, which gives, with the height of the 

 snow-line, the proportion 2 : 3. If then, in respect to latitude, 

 a similar proportion should take place, corn would not be seen 

 beyond 54° of latitude. But in Lapland it is cultivated as far 

 as 68 — 70°. This appears already from the remark of the 

 author, p. liii., viz., that it is very erroneous to suppose that 

 Quito has the same climate as France or Italy ; because, al- 

 though the mean temperature of both places is the same, the 

 distribution of heat is nevertheless very different. 



The author shews, p. li. lii., what families occupy the highest 

 regions in the different zones. In the polar zone, we may very 

 well suppose the Cyperacece to prevail there, on account of the 

 great numbers of Alpine Carices. But when he thinks that,the 

 SaxifragcB are rare in the same region, we cannot agree with 

 him. Wahlenberg's Flora Lapponica contains Alpine species 

 of the genus Saxifraga, and in the above-mentioned Greenland 

 collection, this genus was the most numerous after Carex. 



VII. Determination of those relations of Climate, 



WHICH are most favourable TO ANY OF THE MORE 



COMMON cultivated Plants. (P. Iv. Ivii.) 



Concerning this part I have only to remark, that such views 

 are of the greatest practical advantage ; but that they would 

 probably be much more useful, if the temperature was more 

 accurately given, which might be done in part by means of the 

 above-mentioned curve of temperature. 



As to the result of this examination, to which I have been 

 led by the labours of M. Humboldt, I am unquestionably of 

 opinion, that these treatises, exclusive of many interesting ideas 



• It has already been observed, that this estimate appears too high, 

 t This is the northern limit of birch given in the Flora Lapponica, p. xiv. 



