37 PLEASANT WA YS IN SCIENCE. 



ground in Catalonia, consisting of red and grey sandstone, 

 and in some parts of red marl, almost entirely denuded of 

 herbage, while the roots of the pines, holm oaks, and some 

 other trees, were half exposed, as if the soil had been 

 washed away by a flood. Such is the state of the forests, 

 for example, between Oristo and Vich, and near San 

 Lorenzo. But being overtaken by a violent thunderstorm, 

 in the month of August, I saw the whole surface, even the 

 highest levels of some flat-topped hills, streaming with mud, 

 while on every declivity the devastation of torrents was 

 terrific. The peculiarities in the physiognomy of the 

 district were at once explained, and I was taught that, in 

 speculating on the greater effects which the direct action of 

 rain may once have produced on the surface of certain parts 

 of England, we need not revert to periods when the heat of 

 the climate was tropical." He might have cited instances 

 of such storms occurring in England. For example, White, 

 in his delightful "Natural History of Selborne," describes 

 thus the effects of a storm which occurred on June 5, 1784 : 

 " At about a quarter after two the storm began in the parish 

 of Harpley, moving slowly from north to south, and from 

 thence it came over Norton Farm and so to Grange Farm, 

 both in this parish. Had it been as extensive as it was 

 violent (for it was very short) it must have ravaged all the 

 neighbourhood. The extent of the storm was about two 

 miles in length and one in breadth. There fell prodigious 

 torrents of rain on the farms above mentioned, which 

 occasioned a flood as violent as it was sudden, doing great 

 damage to the meadows and fallows by deluging the one 

 and washing away the soil of the other. The hollow lane 

 towards Alton was so torn and disordered as not to be 

 passable till mended, rocks being removed which weighed 

 two hundredweight" 



We have mentioned the formation of dust, and the 

 action of wind upon it, as a cause tending to level the surface 

 of the land. It may appear to many that this cause is too in- 

 significant to be noticed among those which modify the earth's 



