ON THE SUN'S HEAT. 



375 



which is being continually carried up to the sun's 

 surface and radiated out into space, and of the 

 dynamical relations between it and the solar 

 gravitation, let us first divide that prodigious 

 number (476 x io 21 ) of horse-power by the 

 number (6'i x io 18 ) of square metres 1 in the 

 sun's surface, and we find 78,000 horse-power 



1 A square metre is about lof (more nearly 10764) square feet, 

 or a square yard and a fifth (more nearly 1. 196 square yards). The 

 metre is a little less than 40 inches (39. 37 inches = 3. 281 feet= 1.094 

 yards). The kilometre, which we shall have to use presently, being 

 a thousand metres, is a short mile as it were ('6214 of the British 

 statute mile). Thus in round numbers 62 statute miles is equal to 

 loo kilometres, and 161 kilometres is equal to 100 statute miles. 

 The awful and unnecessary toil and waste of brain power involved 

 in the use of the British system of inches, feet, yards, perches or 

 rods or poles, chains, furlongs, British statute miles, nautical 

 miles, square rod (30^ square yards) ! rood (1210 square yards) ! acre 

 (4 roods), may be my apology, but it is only a part of my reason, 

 for not reckoning the sun's area in acres, his activity in horse-power 

 per square inch or per square foot, and his radius, and the earth's 

 distance from him in British statute miles, and for using exclusively 

 the one-denominational system introduced by the French ninety 

 years ago, and now in common use in every civilised country of the 

 world, except England and the United States of North America. 

 The British ton is 1.016 times the French ton, or weight of a cubic 

 metre of cold water (1016 kilogrammes). The French ton, of 1000 

 kilogrammes, is '9842 of the British ton. Thus for many practical 

 reckonings, such as those of the present paper, the difference 

 between the British and the French ton may be neglected. 



