FOR GENERAL READERS. 



Vol. I. — No. 24. {New Series.) 



FRIDAY, JUNE 15th, li 



r Weekly, Price Sd. 

 L By Post. Sjd. 



Scientific Table Talk 



Furnace for Low-Class Fuel (illus.') ... 



Resistance of Fire 



Remarkable Hail Stones — I. (illus.)... 



The Copper Age in Europe 



General Notes 



Whirlwinds (illus.) 



The Colouis of Twilight 



Blue Milk 



Inequalities of Men ._ 



Natural History: 



Young Tapir in the Zoological 

 Garden at Cologne (ilhts.) 



Pallas' Sand Grouse 



The Smallest Plant in the World 



Miscellaneous Notes 



553 

 554 

 556 

 557 

 558 

 559 

 561 

 562 

 562 

 562 



563 

 564 

 564 

 564 



C ONTENTS . 



The Teaching of Geography ... 



On Death by the Electric Current . 



Reviews ; 



Watts' Dictionary of Chemistry . 

 The Geology of England and 



Wales 



An Elementary Text Book of 

 Practical Metallurgy ... 



Abstracts of Papers, Lectures, etc. : 



Royal Society 



Royal Institution ... 

 Royal Microscopical Society 

 Victoria (Philosophical) Institute 

 Halifa.\- Scientific Society 

 Society of Engineers 



SCIENTIFIC TABLE TALK. 



By W. Mattieu Williams, F.R.A.S., F.C.S. 

 It is difficult to name any subject on which popular 

 fallacies are more generally prevalent than that of arctic 

 climate. If a speaker at an ordinary public meeting 

 were to refer incidentally to the oppressive heat of a 

 sultry summer day in the arctic regions his audience 

 would accept the description as a joke, and be amused 

 accordingly. 



This is not at all surprising, seeing that most of our 

 text books on physical geography, including those that 

 adopt the word " physiography," and are therefore up 

 to the latest fashion, give countenance to the popular 

 fallacy by such exposition as the following, which I copy 

 from one of the most widely circulated books on the 

 subject. 



" The reason why the sun heats the equator and the 

 regions adjoining more strongly than it heats the tem- 

 perate and polar regions is that at the equator it rises 

 higher in the heavens and shines more directly down- 

 wards." This is illustrated by a diagram contrasting the 

 tropical with the polar summer incidence. 



It is true that effect of the solar rays upon a given 

 area of the earth's surface is diminished by obliquity of 

 incidence, and mathematical readers will understand that 

 this varies with the sine of the sun's altitude, and there- 

 fore runs down to zero when the sun is on the horizon. 



Taking this alone, the above quoted paragraph ap- 

 pears to be sound, but there is another factor which is 

 omitted, and this factor is so predominating in determining 

 the peculiarities of arctic climate, that the others are but 

 insignificant. This factor is the length of the arctic days 

 and arctic nights. 



The summer day at the North or South Pole is 365 

 times longer than the summer day at the equator, 6 

 months against 12 hours (omitting the lengthening effect 

 of refraction), and at the polar midsummer the altitude 

 of the sun remains unaltered during the whole 24 

 hours, his apparent path being a circle constantly 

 at 23^ degrees above the horizon. At the equator 

 and other tropical regions when the sun is perpen- 



dicular at midday, he completes his apparent semi- 

 circular path from horizon to horizon in 12 hours, and 

 therefore his mean altitude is but 45 degrees, and this 

 for only 12 out of the 24 hours. Thus we have to com- 

 pare 45 degrees for 12 hours against 235 degrees for 24 

 hours, and this, when worked out for the sines, gives the 

 polar midsummer day an advantage represented by 397 

 against 292, or in round numbers 4 to 3. Therefore, 

 regarding the obliquity of the solar rays alone, the 

 hottest summer climate on the earth is at the poles. 

 The diagram above referred to proves exactly the con- 

 trary to that which is intended. 



I take the above figures from Dr. Zenker's recent work 

 on the Distribution of Heat over the Surface of the Earth, 

 for which, in spite of the nationality of the author, he 

 has received a prize from the French Academy; and am 

 glad of the opportunity of doing so, having been described 

 as a paradoxer for maintaining similar conclusions in 

 the Gentleman' s Magazine, etc. 



My attention was first directed to the subject by 

 practical experience in the course of a visit to merely the 

 fringe of the arctic regions in 1856, when I found the 

 thermometer at 108" in the sun out at sea and 92? in 

 the shade of a cabin built on deck, in latitude 70^* N. It 

 was doubtless hotter on shore. I found it so in the 

 course of an excursion up the Tromsdal, but had no 

 thermometer with me then. 



The figures of Dr. Zenker refer only to the theoretical 

 efficiency of the sun upon the earth, irrespective of the 

 atmosphere which obstructs more or less the passage 

 of the solar heat. The variation of this is more marked in 

 the arctic regions than in the tropics. I had a strik- 

 ing experience of this in the course of a second visit to the 

 neighbourhood of the North Cape in the summer of 

 1875, which was misty and cloudy. The weather was 

 then decidedly cooler than at the same season in England. 



But we must not forget that even the heat which fails 

 to penetrate the misty air is not lost, but is absorbed by 

 the air itself The sun does the same amount of work, 

 but that which fails to warm the surface of the earth is 

 warming the air above it. 



Here in England we sometimes have a few summer 



