IV.] INTRODUCTION. Ixix 



containing a preparation of gold or silver leaf for em- 

 blazoning. The valves of Pecten maximus and P. oper- 

 cularis make an ornamental as well as a useful little 

 dish for scalloped oysters. Ormers are used in Guernsey 

 by farmers to frighten away small birds from the standing 

 corn, two or three of these shells being strung together 

 and suspended by a string from the end of a long stick, 

 so as to make a clattering noise when moved by the 

 wind. Among other services which the Mollusca render 

 to man is their indicating an approach of rain or a 

 change of temperature. Several interesting facts with 

 respect to this hygrometrical property have been recorded 

 by Mr. B. Thomas of Cincinnati, U.S., in Dingler's 

 ' Polytechnisches Journal ; ' and as I am not aware that 

 similar observations have been made or published in 

 Great Britain, I venture to direct the attention of 

 naturalists who live in the country to this curious 

 inquiry. Mr. Thomas states that snails are more 

 reliable than leaves as natural barometers ; that, in con- 

 sequence of their never drinking, all the moisture they 

 receive is by absorption of rain, mist, or dew through the 

 tissues of their bodies, and this they afterwards exude 

 at regular intervals, until they obtain a fresh supply ; 

 that the colour of certain kinds of snail varies according 

 to the quantity of moisture retained; that two days 

 before rain is about to fall they climb trees, which they 

 never do on other occasions ; and that when they are 

 observed to leave the herbage and get on rocks, it is a 

 certain prognostication of wet weather. Not many 

 years ago some wonderful stories were afloat as to the 

 galvanic nature of snails, which it was proposed to 

 turn to account as a medium of communication between 

 distant friends ; but this mystery has been eclipsed by 

 that of spirit-rapping, with which the molluscan phe- 



