3 82 



NATURE 



\_August 17, 1882 



Shade Temperatures at Noon and Different Altitudes 



Height 





Station. 



Oatlands Park 

 Riffelberg 



Hornli 



Gornergrat 



Whitby 



Aak, Romsdal 

 Pontresina 

 Bernina Hos[ itz 

 Diavolezza 



Bellagio ... 



Shiahorn 



Schwarzhorn ... 

 Hence it follows that the difference of solar intensity between 

 noon and sunrise and sunset respectively is less at great than at 

 small elevation*, a deduction which is substantiated by the ex- 

 perimental data contained in the following table : — 

 Variation of Solar Intensity at Different Hours. 



Station. 



Isle of Wight 



Riffelberg (8, 428 ft.).. 

 Gornergrat (10,289 ft.) 



Similar testimony is also afforded by a comparison of early 

 and late observations at widely different altitudes : — 

 Variations of Solar Intensity at Different Altitudes 



Solar 



Intensity. 



°C. 



286) 

 37'2( 

 3°'3 I 

 49"2 S 



D.fference 



io'6 



The sun's altitude was unfav. urable for the comparison ; 

 nevertheless, there were here observed differences of 8'6° C. 

 and io'6°. 



The farther we recede from the earth, the nearer we realise 

 the conditions >_f solar radiation altogether outside the limits of 

 the atmosphere, where the solar intensity (assuming the sun's 

 emission to remain constant) is uniform from sunrise to sunset. 

 Throughout the dreary winter days, when, even in the country, 

 a leaden sky oppresses us it is tantalising to reffect that, at the 

 moderate height of 5,000 feet, which can be reached by a 

 balloon in a few minutes, there is probably blue sky and brilliant 

 sunshine. 



Latitude profoundly, ihough irregularly, affects air tempera- 

 ture, for in high latitudes less solar heat falls upon each square 

 foot of the earth's surface, and therefore the air resting upon 

 that surface is warmed to less extent. But obliquity of the sun's 

 rays has no such influence on solar intensity, for the highest 

 readings of solar heat at or near sea-level have been observed 

 near to the Arctic circle, as is seen from the following table : — 

 Solar Intensity in Different Latitudes. 



Sun's Sun Tern- Solar 



Altitude, perature. Intensity. 



Station. 



Latitude. 



These results show that, with an obliquity of only 6°, the sun 

 temperature and solar intensity were respectively only 789° and 

 487° C. ; whilst with an obliquity of 41°, there were S2'5° and 

 487° C. On the equator at noon, with a nearly vertical sun, the 

 solar intensity was actually 7° C. lower than in Romsdal, only 4 j 1 . 

 of the Arctic circle. On the other hand, air warmth diminishes, 

 as a rale, with increase of latitude, although, as the following 

 table shows, there are some remarkable exceptions, for it was 1° 

 higher in lat. 52° N. with an obliquity of 29°, than in lat. 5° N. 

 with an obliquity of only 12°, and in the high latitude 63, with 

 an obliquity of 41°, it was only i°C in arrear of the air-warmth 

 at the equator with an obliquity of only 6°. 



Shade Temperature at or near Noon and Sea-Level. 



At Sea, April 10 



,, March 23 



.. .. 22 



„ 18 



„ 17 



., 16 



., 13 



,, Feb. 24 .. 



,, ,, 20 ... . 



„ 19 ... . 

 „ 16 ... . 

 ,, Jan. 27 ... 



Bellagio, Sept. 17 ... 

 Oatlands Park, June 8 . 

 Isle of Wight, May 13 . 

 ,. 14 

 ., 15 

 Whitby ... Aug. 16 . 

 Aak, Romsdal, July 15 . 



45 S. 

 3' .. 

 29 „ 

 27 .. 

 23 .. 



20 ,, 

 11 >> 

 10 ,, 



9 .. 

 o ,, 

 3 N. 

 5 ., 

 8 ,, 

 17 ,. 



21 ,, 

 23 .. 

 3° ,, 

 5' .. 

 45 .. 

 52 „ 

 5i .. 

 5i .. 

 51 .. 

 54 ., 

 63 „ 



37 

 58 

 60 



65 



68 



71 

 82 

 83 

 85 

 84 

 Si 

 78 

 75 

 64 

 58 

 56 



57 

 58 



58 

 50 

 49 



189 

 263 

 297 

 32-5 

 328 

 294 

 37-2 

 37 - 2 

 36-5 

 37'2 

 30-0 

 294 



317 

 28-0 

 28-3 

 27-2 

 2S9 

 io-6 

 285 

 300 

 28-9 

 29-0 

 300 

 32-0 



36 '2 



Shortly summarised, therefore, the conditions most favourable 

 for a genial climate — 



Depending on solar intensity 

 are — 



1. Great elevation above sea- 

 level. 



2. A light coloured ground 

 and back-ground. 



3. Shelter. Reception of 

 direct and reflected rays. 



4. A clear sun with white 

 clouds. 



5. A clean atmosphere. No 

 dust, smoke, or fog. 



6. A minimum of watery 

 vapour in the air. 



Depending on air tempera- 

 ture, are — 



1. Slight elevation above 

 sea-level. 



2. A dark coloured ground 

 and back-ground. 



3. Shelter. Reception of 

 direct and reflected rays. 



4. A clear sun with white 

 clouds. 



5. A clean atmosphere. No 

 dust, smoke, or fog. 



6. A maximum of watery 

 vapour in the air. 



Thus whilst there are three conditions common to both cate- 

 gories, the three remaining ones are diametrically opposed to 

 each other. 



Town Climate. 



The climate of towns defends upon the same essential condi- 

 tions as that of the country, but some of these are more within 

 our own control in towns. 



The great evils of our town climate are excessive heat in 

 summer and cheerless gloom in winter. We suffer less, however, 

 from excessive solar intensity than continental cities between the 

 same parallells of latitude, owing to the very causes which 

 plunge us into a more miserable gloom in winter. Light-coloured 

 walls neither make our streets look cheerful nor feel hot. Such 

 sad colours as brick, stone, stucco, or paint give to cur hou-es 

 are soon changed to a grimy neutral tint, powerless to reflect 

 either solar light or heat. 



The darker the colour of the houses, the cooler the streets and 

 the hotter the rooms during sunshine, and vice versa. Whilst the 

 summer climate in our streets and houses is thus, to a consider- 

 able extent controllable, that of winter, which depends so much 

 on a clean atmosphere, is still more so. All our towns are nearly 



