362 EETURN TO BOSTON. [CHAP. XL. 



the salts expelled are still contained in air-cavities 

 and cracks, or form thin films between the layers of 

 the ice, these entangled salts cause the ice to melt 

 at a lower temperature than 32, and the liquefied 

 portions give rise to streams and currents within the 

 body of the ice, which rapidly carry heat to the in 

 terior. The mass then goes on thawing within as 

 well as without, and at temperatures below 32 ; 

 whereas pure and compact Wenham ice can only 

 thaw at 32, and only on the outside of the mass. 



Boston, May, 23. Sir Humphrey Davy, in his 

 &quot; Consolations in Travel,&quot;* has said, that he never 

 entered London, after having been absent for some 

 time, without feelings of pleasure and hope,; for there 

 he could enjoy the most refined society in the grand 

 theatre of intellectual activity, the metropolis of the 

 world of business, thought, and action, in politics, 

 literature, and science. 



I have more than once experienced the same feel 

 ings of hope and pleasure after having wandered 

 over the less populous and civilised parts of the 

 United States, when I returned to Boston, and never 

 more so than on this occasion, when, after travelling 

 over so large a space in the southern and western 

 States, we spent ten days in the society of our literary 

 and scientific friends in the metropolis of Massachu 

 setts, and in the flourishing university in its suburbs. 

 They who wish to give a true picture of the national 

 character of America, what it now is, and is destined 

 to become, must study chiefly those towns which 



* P. 168. 



