3iH0 On the Praclicalilitij 



tiniate and simple agencies. These operations, from tlieir sim- 

 plicity, although great and momentous in their results, often 

 escape the observations of man, till, after a long succession of ages, 

 changes are effected, the cause and origin of which are for ever 

 hid from mortal research. The parent-shoal of these herrings 

 may have passed from the sea into the lake at a very early pe- 

 riod, when the waters of the latter might be less elevated above 

 the Clvde, perhaps aided by the circumstances of a flood in the 

 river and a spring-tide from the sea. This might throw the 

 waters so far back, as to render the pressure of the current from 

 tiie lake little beyond the run of a brisk ebb. 



The lierrings once fairlv in the lake, might not so easily escape 

 from their new element by the narrow and single outlet where 

 the water runs with some force. In the regular migrations of 

 herrings from the bays and shoals to the depths of the ocean, in 

 their endeavours to escape from the still waters of tlie lake, ar- 

 riving at where the current acquires its greatest force, they might 

 instinctively spring back, from the dread of impending danger or 

 any sudden impulse, and seek safety in the still waters and depths 

 of the lake, where, in time, they have become as completely na- 

 turalized to tl.e fresh, as they were originally to the salt water. 



[Loch Leven in a future paper,] 

 Mai-ch23, 181S. G. IngLIS. 



LVIII. On (lie PracLicahilily of a direct Passage over the North 

 Pole. 



[Continued from p. 306.] 



eluDGiNG from such facts as are before us, that a part, and but 

 a very small part, of the demand to supply the southern current, 

 comes in from the Pacific through Behring's Strait, — it is neces- 

 sary to inquire, From what sources, then, is all the water so flow- 

 ing out ol the Polar regions to tlie southward derived ? 



I have supposed them to be produced (at least the •'' motion 

 of the great deep," generally) by evaporation in the equatorial 

 regions of heat, and by cold returned, in various ways, in the at- 

 mosphere by land and by sea, into all the northern regions, even 

 as far as the Pole. For though " the way of the Almighty," as 

 thr psalmist savs, "■ is on the sea, and his path in the deep wa- 

 ters," yet it is also as surely in the clouds of heaven. And though 

 *' his footsteps are not known" certainly, yet it is permitted us 

 hunil)Iv to endeavour to trHce them. 



Whether or not there is any increase of water from the melting 

 of the ice in tiie Polar sea so as to cause a current to the south, 

 appears to be not very material; and perhaps has little to do in 



increasing 



