178 Mr. Charles Tomlinson 



on 



draw down cold air from above, or draw up warm moist air 

 from below, in either case supplying some at least of the con- 

 ditions for the generation of hail. The diminution of the 

 temperature of the air with the altitude may be roughly stated 

 as one degree F. for every 343 feet of ascent, and the point 

 of perpetual congelation at and above the equator 14,000 feet ; 

 at 30° 12,000 feet; at 40° 10,000 feet ; at 50° 8000 feet ; 

 at 60° 6000 feet ; at 70° 4000 feet ; at 80° 2000 feet, and 

 after this the point rapidly approaches the earth. 



Prof. Olmsted's theory has been admirably elaborated by 

 the officers of the United States Coasts Survey, as will 

 presently be noted. In the meantime a few cases may be 

 cited to show how the idea gradually became developed into 

 the present consistent theory. Thus Mr. J. C. Martin 26 , of 

 Pulborough in Sussex, writing in 1840, refers to masses of 

 ice having fallen five, six, and seven inches in circumference, 

 and goes on to state that there can be only one way by which 

 such masses are suspended in the air long enough to grow to 

 such a size, and that is by the assistance of a nubilar whirl- 

 wind or waterspout. He states that he once witnessed an 

 appearance of this sort between a higher and a lower cloud, 

 that had a strongly electric aspect before they had resolved 

 themselves into nimbus. It was a bent massive column of 

 dark vapour in rapid rotatory motion, passing from one cloud 

 to the other, continuing for some minutes, and gradually 

 disappearing. The hailstones are described as spheres 

 flattened at the poles, the result of rotatory motion. In a 

 hail-storm which devastated Dublin on April 18th, 1850 27 , 

 some observers state that they saw two strata of oppositely 

 electrical clouds and discharges passing between them, and 

 that the hailstones were as large as pigeons' eggs, and were 

 formed of a nucleus of snow or sleet, surrounded by transpa- 

 rent ice ; this was succeeded by an opaque white layer, 

 followed by a second coating of ice, and, in some examples, 

 five alternations were counted. The storm is described as a 

 cyclone, but Mr. Piddington, in quoting it, prefers to call it a 

 tornado. He also remarks on a common entry of the logs of 

 ships, which have been involved in cyclones, and especially if 

 near the centre, of " rain as cold as ice," " sea-water warm, 

 rain bitterly cold ; " also, " rain accompanied by sleet/'' 

 In the account of the " Duke of York's " cyclone, the entry 

 occurs twice — " Cold most intense during the hurricane." 

 The enormous force with which hail is sometimes projected 

 almost horizontally indicates a force very different from 



26 Quoted in Piddington's Sailor's Horn-Book, 1860. 

 2 " Ibid. 



