RET 



RET 



RESULTING use, in law, is when an 

 use limited by a deed expires, or cannot 

 vest, it returns back to him who raided it. 

 See USES. 



RETAINER of debts, an executor, 

 among dtbts of equal degree, may pay 

 himself first, by retaining in his hands the 

 amount of his debt. 



RETARDATION, in physics, the act 

 of diminishing the velocity of a moving 

 body. If bodies of equal bulk, but of dif- 

 ferent densities, be moved through the 

 same resisting medium, with equal velo- 

 city, the mtdi'.m will act equally on each, 

 so that they will have equal resistances, 

 but their motions wil be unequally retard- 

 ed, in proportion to their densities Re- 

 tarded motion from gravity is peculiar to 

 bodies projected upwards," and this in the 

 same manner as a failing body is accele- 

 rated ; only in the latter, the force of gra- 

 vity acts in the same direction with the 

 motion of the body : and in the former in 

 an opposite direction. As it is the same 

 force which augments the motion in the 

 falling, and diminishes it in the rising bo- 

 dy, a body will rise till it has lost all its 

 motion ; which it does in the same time 

 wherein a body falling would have ac- 

 quired a velocity equal to that wherewith 

 the body was projected upwards. 



RETE mucosum, in animal economy, is 

 the mucous substance, situated between 

 the cutis vera and epidermis, its compo- 

 sition cannot be determined with preci- 

 sion, because its quantity is too small to 

 admit of examination. It is known that 

 the black colour of negroes depends upon 

 a black pigment, situated in this sub- 

 stance. Oxymuriafic acid deprives it of 

 its black colour, and renders it yellow. 

 A negro, by keeping his foot for some 

 time in water impregnated with that acid, 

 deprived it of its colour, and rendered it 

 nearly white ; but in a few days the black 

 colour returned again with its former in- 

 tensity. This experiment was first made 

 by Dr. Beddoes, on the fingers of a ne- 

 gro. 



RETENTION. Whatever be the ef- 

 fect produced in the mental organs by the 

 impressions on the organs of sense, that 

 effect can be renewed, though in general 

 with diminished vigour, without a repeti- 

 tion of the sensible impressions. In other 

 words, sensible changes produce a ten- 

 dency to similar changes, which can be 

 repeated without the repetition of the 

 external impressions, and may then be 

 called ideal changes. Less generally sen- 

 sations leave relicts behind them, which 



can be perceived without the agency of 

 the external organs of sensation, and 

 which are called ideas. The power or 

 capacity of the mind, by which tendencies 

 to ideal changes are retained, may be call- 

 ed the retentive power. 



That tendencies to a repetition of sen- 

 sorial changes are thus formed, that ideas 

 are thus retained, may be referred to the 

 operation of the associative power, and in 

 the human being they certainly depend 

 upon the same organic causes, whatever 

 those be. But in many animals it is decid- 

 edly probable that sensations leave no re- 

 licts bthind them ; and in man there are, 

 equally probably, numerous impressions 

 from external objects, which leave no re- 

 licts behind them. Again, these relicts 

 of sensations can re -appear without the 

 agency of external objects. Hence it ap- 

 pears preferable to consider the receiv- 

 ing of sensations, and the retaining of 

 ideas, as two separate, though intimately 

 connected operations, and as implying- 

 two separate powers or capacities of the 

 mind. This is not done bv Hartley, who 

 appears to refer both to sensation ; but 

 it has subjected him to some apparently 

 just, though in reality unfounded animad- 

 versions of the great northern philoso- 

 pher, Dugald Stew art. Speaking of the 

 phenomena of memory as not to be en- 

 tirely explained by the law of associa- 

 tion, he says, (p. 4-12.) " The associa- 

 tion of ideas connects our various 

 thoughts with each other so as to pre- 

 sent them to the mind in a certain or- 

 der, but it presupposes a faculty of re- 

 taining the knowledge we acquire.** 

 This Hartley knew, and has according- 

 ly a distinct section on the generation of 

 ideas. 



Without the retentive power it is ob- 

 vious that man would be a being of 

 mere sensation, little, if any, superior 

 to the lowest orders of the animal cre- 

 ation, and inferior to many of them. 

 The retentive power provides materi- 

 als for the agency of the associative pow- 

 er. Without the retentive power the 

 associative power would never be call- 

 ed into exercise, and without the associa- 

 tive power, the relicts of sensation, the 

 effects of the retentive power would 

 be of no utility. The operations of the 

 retentive power can scarcely be sepa- 

 rated from those of the associative pow- 

 er, which together constitute the com- 

 pound faculty called memory, for an ac- 

 count of which see PHILOSOPHY, mental, ^ 

 105. 



We have said that the receiving of SCR - 





