Biographical Account of the late John Dalton. 03 



mean to be 31 inches, and to this adding the dew (reckoned at 5 inches), 

 we have for the mean quantity of rain in England, 36 inches annually. 

 The most rainy place is Keswick, in Cumberland, where the quantity of 

 rain that falls annually is 67J inches. 



Thus the annual fall in England amounts to 28 cubic miles, or 115,000 

 millions of tons. This immense mass, since it does not accumulate, must 

 be annually carried off by evaporation, and by rivers. 



From a somewhat loose estimate, he reckons the water carried to tho 

 sea by all the rivers in England, to amount annually to 13 inches, or 10 

 cubic miles, or 41,000 millions of tons. 



From the experiments of Dr. Dobson of Liverpool, and from a set 

 made by himself and Mr. Thomas Hoyle, he concludes that the evapora- 

 tion amounts annually to 30 inches. Thus the rivers and evaporation 

 together, amount . to 43 inches. This exceeds the rain by 7 inches. 

 This difference he considers as only apparent, and owing to inaccuracy in 

 tho experiments. 



I believe the true cause of the discordance is, that he estimates the 

 quantity of water thrown into the sea, by rivers, too high. Instead of 13 

 cubic inches, it does not amount, I conceive, to more than 6 inches. 



Mr. Dalton began very early to pay particular attention to meteorology. 

 He began a meteorological register when at Kendal, and continued it to 

 the very last year of his life. In 1793, soon after going to Manchester, 

 he published a small book, to which he gave the name of Meteorological 

 Observations and Essays. A second edition of this book was published 

 by him in the year 1834. This second edition was a re-print of the first, 

 but there was an appendix added, containing 60 octavo pages. 



The only part of this book which seems to require attention in this 

 brief abstract, is his theory of the Aurora Borealis. 



He demonstrated, by the application of mathematical principles to the 

 phenomena of the Aurora Borealis, that the luminous beams of the Aurora 

 are cylindrical, and parallel to each other, and to the magnetic meridian 

 of the earth ; that tho height of the rainbow-like arches of the Aurora, is 

 about 150 miles; that the beams are similar, and equal in their real 

 dimensions, and that the distance of the beams from the earth's surface 

 is nearly equal to their length. The light he considered as electrical, 

 and the beams themselves of a ferruginous nature. He conceives that 

 there exists in the higher regions of the atmosphere, an elastic fluid 

 partaking of the properties of iron, to which the phenomena of the 

 Aurora Borealis are owing. It is unnecessary to discuss this opinion, as 

 the discoveries in electricity and magnetism made since 1793, render tho 

 opinion unnecessary. 



The discovery for which Dalton is indebted for the high reputation 

 which he obtained in this country, is what is called The Atomic Theory. 

 As the history of this great discovery is very imperfectly known in this 

 country, it will be necessary to enter somewhat into detail. 



In the year 1792, Richter published a treatise, to which he gave the 



