234 WANT OF OBSERVATION. 



more dangerous ; for, just as at sea there is more 

 to be dreaded from the sunken rock, than from 

 that which stands high and gives warning, so in 

 the case of error, there is ever the more peril from 

 that which is the more concealed, or has the nearer 

 resemblance to truth. 



We find that very frequently the case in mat- 

 ters connected with the study of nature more 

 especially those parts of nature which do not ap- 

 pear to bear immediately upon the common con- 

 cerns of food and clothing. In those very lichens, 

 which we have mentioned, as being useful in dye- 

 ing, it is not the people who live where they grow 

 that gather them, but strangers who find it their 

 interest to go there in the season : so also it is not 

 very long since the people of Britain depended 

 mainly upon the Dutch for supplies of the very 

 fish, which are most plentiful on the British 

 shores. 



In matters connected with the earth itself, the 

 want of common observation, and the loss occa- 

 sioned by that want, are still more striking. If 

 coal, or iron, or any other useful mineral, is 

 found for the first time in any district, it will, in 

 general, be found that the discoverer is not a na- 

 tive, but some stranger. There is a case in point. 

 The greenstone rocks, which form a considerable 

 portion of the lower valley of the Tay, contain 

 vast numbers of veined agates or Scotch pebbles, 

 and in some places the rock has, to a considerable 

 depth, crumbled into mould, well fitted for agri- 

 cultural purposes ; but the pebbles, containing less 

 clay than the stone in which they have been 

 formed, and being of a close texture, do not de- 

 compose so readily. In consequence there are 



