34 INTRODUCTION. 



tained, and which are originally due either to igno- 

 rance or superstition ; or by a bias affecting our own 

 minds individually, and caused by a peculiar train of 

 thinking into which we have fallen. The first class 

 of prejudices are those which prevail so frequently 

 with persons of slender education and weak abili- 

 ties, who readily embrace whatever notions have 

 been handed down to them by their forefathers, 

 without troubling themselves to inquire whether 

 they are correct or not. These hindrances to the 

 diffusion of true science are gradually dying away, 

 as knowledge spreads, and education advances, 

 and we hope in a few years most of them will be 

 extinct. But they still in many instances main- 

 tain an obstinate hold over the mind, utterly in- 

 capacitating it for investigating the truth. When 

 due to superstition, they are, as White observes, 

 sucked in, as it were, with our mother's milk, and 

 growing up with us at a time when impressions 

 generally take the most lasting hold, become so 

 interwoven into our very constitutions, that the 

 strongest good sense is required in order to dis- 

 engage ourselves from them.* Every one's memory 

 will supply them with instances of this class of pre- 

 judices, of such frequent occurrence in respect of 

 matters of Natural History, that it is needless to 

 particularize. But we guard all persons, wish- 

 ing to become observers, against their influence. 

 We require them to dismiss every notion from their 

 minds, imbibed from others, until they have taken 

 correct steps to verify it, and to go forth into the 



* Letter xxviii. to Dairies Barrington. 



