Feb. 5, 1S85] 



NA TURE 



325 



climate with sudden changes uf temperature, as, fur instance, in 

 the United States, does not suit this plant. On the banks of the 

 Ohio River the fruits are rotten, or fall down, before they are 

 ripe, notwithstanding that the mean temperature of all the months 

 at Cincinnati is higher than at Pesth in Austria ; but the Ameri- 

 can species are cultivated with success. 



In California, with its equal temperature, the vine is culti- 

 vated, though the mean temperature at San Francisco is much 

 lower than in Europe in the same latitude ; but the dry Cali- 

 fornian summer is not to be found throughout the United States, 

 where heavy rains occur at this season. 



Everywhere, in the warm as well as in the temperate regions, 

 corn is cultivated with success where there is in summer direct 

 sunlight enough to ripen its grains : on the highlands of Af- 

 ghanistan, in China, on the plains of Southern Russia, on the 

 highlands of Mexico, &c. — for these plants require also the 

 direct solar warmth. 



On highlands the influence of insolation is very much in- 

 creased. At Leh, in Tibet, altitude about 12,000 feet, the 

 thermometer rose in July, in the sun, to 144°, and in mid-winter 

 to S4 , though the mean summer temperature is only 61°, and 

 that of the winter 16°. ' Barley is sown about May 18 and har- 

 vested on September 12; but in the valley of Pituk (altitude 

 about 11,000 feet) barley was sown and harvested in two 

 months. 



But, in the first place, the solar warmth of the after summer is 

 necessary to ripen the fruits of the most important plants ; for 

 the vine a September temperature of at least 59° is thought to 

 be necessary (Greisbach, "Die Vegeta.ion der Eide," theil i. 

 p. 126). Now, if we compare the means of this month of certain 

 places in Southern England (Greenwich 57°, Penzance 57 , 

 Chiswick 57 , Isle of Wight 58°) with others on the Continent 

 (Liege 6i°, Mannheim 62), we see it is clear that the cloudy 

 sky and rain, and not the mean temperature, are the causes of 

 the vine being cultivated without success in England. 



The limit of corn cultivation ascends on the Continent gene- 

 rally farther to the north than on the shores — Fort Norman 

 (X.W. Territories of Canada) 65°, Jakutsk 62 . 



The fact of its reaching 70° N. lat. in Norway (Alten), and 

 the impossibility of agriculture in Greenland, even under do\ and 

 in Iceland (Reikiavik), notwithstanding the mean summer tem- 

 perature of Alten and Reikiavik being about equal,- can only be 

 explained by the continual clear sky in summer at Alten, 

 and by the powerful insolation here, which is not the case in 

 Iceland. The continual wet climate and absence of sunlight 

 make the grains rot on the stalks before they are ripe 

 (Martins, " Essai sur la Vegetation de l'Archipel des Feroe," 

 pp. 388, 392). The period of vegetation at Alten is the same as 

 that in Siberia (Jakutsk), though the mean summer temperature 

 is 9° lower. 



But a climate such as that of Northern Norway, where the 

 shores are free of ice even in mid-winter, caused by the north- 

 east branch of the Gulf Stream, is nowhere to be found on the 

 globe under such a high latitude. On the north-east shores of 

 Asia corn cannot be cultivated even under 50° N. lat. The same 

 latitude is its limit on the eastern shores of America ; on the 

 western it reaches about 57'. On the north-east shores of Asia 

 the cause is the ice in the sea of Ochotsk, the wind in summer 

 being mostly south-east or south, 3 thus coming from the sea or 

 along the shores, and causing much lower summer temperatures 

 than in the interior, 4 and cloudy sky. On the north-east shores 

 of North America the corn limit reaches 50 N. lat., the cause 

 being here the ice in Hudson Bay and along the shores of 

 Labrador and Newfoundland. 5 But again, it is not alone the 

 low mean tempeiature which causes the corn limit to descend so 

 far southerly, but want of sunlight. 1 ' 



I lis observe J in September, and lasts till the end of May. See 

 Moorcroft, "Travels in the Himalayan Provinces." 



' Summer temperature at Alten ~^\ at Reikiavik 54 . See Dove, "Tern- 

 peraturtafeln." 



3 On account of the barometric summer minimum over the Asiatic continent. 



4 Temperature of Ochotsk, lat. 59° 21': June 46 , July 55 , August 56 , 

 September 47°. Temperature of Nicolajefsk, lat. 53 8' : June 54", July 61", 

 August 6l°, September 50". See Schrenck, " Reise im Amur Lande," bd. iv. 

 p. 405. 



5 Mean temperature in 1876 at York Factory, lat. 57 : June 40°, July 57°, 

 August 55°. Mean temperature in 1S80 at Moose Foil. Ontario, lat. 51 16 : 

 June 55", July 59', August 55', September 52°. See Report of the Meteoro- 

 logical Service in Canada. 



ttaeeof sky clouded, Nikolajefek of the Amur: June 58, July 59, 

 August 63. See Schrenck, " Reise im Amur Lande," bd. iv. p. 476. Per- 

 centage of sky clouded in 1880 :u Moose Fort : June 66, July 

 62. Number of rainy days : June 15, July 15, August 20. See Refcrt of 

 1 ; oroli igical Sen ice in Canad .£ 



In the vicinity of the arctic zone the influence of insolation is, 

 in the first place, observed on the Continent. At Turuchansk, 

 lat. 65° 55', gourds are cultivated, though of a small size (Mid- 

 dendorff, " Sibirische Reise," band iv. theil i. p. 701). The mean 

 temperature in 1S81 was : Of June 48°, of July 59°, and of 

 August 55°, the two last months being about equal in tem- 

 perature to the means of Valentia in Ireland, lat. 51° 55' (July 

 59 , August 59 ) ; but at Turuchansk there were, in June, 7 

 days with the temperature, at I p.m., ranging between 68° and 

 73°; in July, 15 days ranging between 68° and 82°; and in 

 August, 16 days ranging between 62° and 75°. Number of 

 days completely clouded : June 6 ; July 9 ; August 3. Snow 

 did occur till June 15, and was observed again on August 

 29 (Annalen do- Physikalischen Central Observaloriums, St. 

 Petersburg). In Norway the cultivation of gourds (Cucurbita 

 Ptfo, L. ) reaches 59" 55'. 



In North America, at Cumberland House, lat. 53° 57'> a 

 sugar harvest is collected from Negitmio fraxinifolium, Nutt. 

 {Acer negumio, L. ), by means of cuttings in the trees, but the flow 

 of the sap is greatly influenced by the action of the sun's rays, 

 and is greatest after a smart night's frost (Richardson, 

 "Search Expedition through Ruperts Land," vol. ii. p. 236). 



In summer, the influence of the direct sunlight causes the 

 tropical mid-day temperature so common in the interior of both 

 continents in the temperate zone ; but in America the days' 

 differences are much greater than in Asia ; ' even near the eastern 

 shores (Montreal, Quebec, &c.) daily differences of 20 are of 

 common occurrence in midsummer. 



The Asiatic continent, reaching to the Arctic Sea, without in- 

 terruption presents to the sun's rays a much greater surface 

 than is the case with America, where the melting ice in 

 Hudson's Bay and the Arctic Archipelago consumes the greatest 

 part of the solar warmth, being at the same time the cause of 

 the sudden low temperatures occurring when the wind turns to 

 the north or north-west. 



Notwithstanding this, the European vegetables and corn are 

 cultivated with success in the United States and the interior of 

 Canada, but some of them cannot stand the sudden changes of 

 temperature, as, for instance, the vine, and also the orange-tree 

 {Curus aurantium, L., et varr.) ; the general cultivation of the 

 latter does not reach beyond 30° N. lat. (Florida). 



Nowhere else is the influence of insolation more distinctly 

 observed than in the arctic regions. It is known that in high 

 latitudes the heat of the sun's rays in summer is often very 

 great. Richardson remarks that (being under about 6o° N. lat. 

 near the Slave River) he had never felt the heat within the 

 tropics so oppressive as he experienced it on some occasions 

 in these arctic regions (Richardson, "Search Expedition," 

 vol. i. p. 144), though the sun's rays are here always horizontal 

 instead of vertical, as is the case in the tropical countries. The 

 enormous multitude of mosquitoes suddenly appearing in spring 

 when the ice is thawing, and in places where there is water for 

 their larva; (swamps, pools, &c), is also much greater than in 

 India. 



The observations on the following page may give some idea of 

 the difference between the temperature in the shade and that in 

 the sun's rays. 



At Fort Franklin, Great Bear Lake, North America, lat. 

 65° 12', the mean temperature in the last part of March or the 

 beginning of April is about o° F. ; the effect of the sun's rays on 

 the blackened bulb of a thermometer, however, is sufficient to 

 raise the mercury to 90^ (Richardson, "Search Expedition," 

 vol. ii. p. 254). 



Comparing these observations with those within the tropics 

 we see that the difference between the maximum temperature in 

 the sun in these regions and the northern is relatively small. 

 Maximum temperature in the sun, 1882 : Calcutta, 162 ; 

 Bombay, 151° ; Colombo (Ceylon), 157° ; Barbados, 156°. But 

 in dry climates the difference is greater : Melbourne, 169 ; 

 Adelaide, lSo°. The mean humidity at Adelaide was only 

 58 per cent. ; highest temperature in shace 112°. 



Even in the North American Arctic Archipelago, in Smith 

 Sound, lat. 78 30', where the mean summer temperature is only 

 t,^ (June 30°, July 38°, August 3ii°), Kane's observations 

 with the black bulb thermometer gave the following results : — 



1 Greatest difference at Winnipeg, lat. 49 55', on July 2, i38i, maximum 

 98°, minimum 45° ; difference 53°. At Poplar Heights. Manitoba, lat. 50 5', 

 maximum on May 20, 86°, minimum 27° ; thus difference 59°. At Blagowescht- 

 schensk, Siberia, lat. 50" 15', on May 25, 1881, maximum 79°, minimum | I : 

 difference 31°. At Akmolinsk, lat. 51 12', on May 25, maximum 63 , mini- 

 mum 50 ; difference iS° 



