334 Mr. Toulmin Smith on the different Beds 



Centurus tricolor, Gmel. (Woodpecker, Spotted.) s. 



" Native, and the most domestic of its tribe ; I have lately shot 

 them tapping at the facings around the corners of this dwelling- 

 house. Feed like all the tribe upon insects ; but this species is 

 particularly noted for destruction to the Indian corn when in a 

 soft and milky state, and may then often be found with the cele- 

 brated corn thief the Tanager (Tachyphonus leucopterus). In 

 making this accusation against this species, I am inclined to think 

 that while tearing the ears of corn and exposing them to the 

 rain, &c, it is more with a view to secure ants than to destroy 

 corn, as a great many ants are in general collected around the 

 ears once exposed in that soft state. They have two different 

 notes, the regular response being a prolonged whistle, sharp, 

 strong and piercing, at first slow, about sixteen times repeated, 

 quick towards the middle and again prolonged towards the con- 

 clusion." 



[To be continued.] 



XXXII. — On the different Beds of the White Chalk, and on the 

 Faults and Dislocations which they exhibit. By J. Toulmin 

 Smith, Esq. 



It is certainly no less true of geology than of any other branch 

 of natural science, that it is endangered as much by " false facts 

 as false theories." Such " false facts n are not merely neutrally 

 mischievous : they are fertile sources of positive error and erro- 

 neous induction. Even if the true character of the " false fact " 

 is perceived, it will often not be till it has added much to that 

 labour which every true naturalist must oftentimes undergo of 

 u laboriously groping about in the dense labyrinth of facts *." 



I called attention some months ago to an important instance 

 of such a " false fact w very authoritatively put forth as to the ex- 

 istence in one geological sera of one of the most extraordinary crea- 

 tures which geological research has yielded — the Pterodactylef. 

 It is important to my present purpose to repeat this instance, as 

 it originated in a very common source of such false facts, and one 

 against which the most able inquirer has no defence if he depend 

 for his material on the dealer instead of obtaining it as the re- 

 ward of the personal exploration in the field of himself or of a con- 

 fidential collaborator. Many other instances might be cited of 

 positive error which has in this way been promulgated, or in 

 which the danger of promulgating still greater and more sweep- 



* Oken's preface to the Ray Society's ed. of his ' Elements of Physiophi- 

 losophy.' 



f See vol. xix. of this Journal, p. 295, note. 



