14 INTRODUCTION. 



To olserve well is not so easy a thing as some persons imagine. 

 Some are too hasty, imagining that they can take in everything 

 at a glance, and often forming very erroneous or imperfect 

 notions. Others are too slow, fixing their attention too exclu 

 sively on the details, so as to lose sight of the general plait. 

 Both these faults should be carefully avoided ; and the habit of 

 guarding against them, once acquired, will be of invaluable 

 service in future life. There is also a danger in allowing our 

 observations to be influenced by previously formed ideas; so 

 that we often think we see what exists only in our own imagina- 

 tions. This habit cannot be too early checked ; and there is 

 probably no better mode of preventing its formation, than the 

 accustoming the young to exercise their organs of sense upon the 

 numberless objects which the study of Nature brings under their 

 notice, and to give careful and accurate descriptions of what they 

 observe. It has been sometimes said that there are more false 

 facts, than false theories, in science ; and if this is true of any 

 department, it is of Natural History. It is wonderful how the 

 most acute and profound reasoners have erred, when they have 

 trusted too much to their own observations, and too little to the 

 statements of others, who may have been much more competent 

 than themselves as observers, though far inferior as reasoners. 

 This was not unfrequently the case with the great Bacon ; who, 

 so far from contributing anything to our knowledge of facts in 

 Natural History, often gave additional force to errors by the 

 weight of his authority. Many examples of this will be found 

 in his treatise entitled " Sylva Sylvarum ;" the following will 

 here suffice. 



The Misseltoe is included by Bacon among the excrescences, 

 which sometimes grow from trees as a consequence of disease. 

 " They have an idle tradition," he says, " that there is a bird 

 called a missel-bird, that feedeth upon a seed, which many times 

 she cannot digest, and so expelleth it whole ; which, falling upon 

 the bough of a tree that hath some rift, putteth forth the Missel- 



