Page:The New International Encyclopædia 1st ed. v. 10.djvu/781

* INTENSITY OF SENSATION. 693 INTENT. lute sightlessness, as the 'idio-aural noise' pre- cludes absolute silence. For external stimulation, the brightness limen may be put at the illu mination of black velvet by a stearin candle nine meters distant. It is sometimes esliniat(-d (though too high) at 1/300 the light of the full rcoon. In one-half second this light exerts upon the retina the energy required to raise 1/15 nig. of water one billionth of a degree C. For the liminal sensitivitj- to articular sensations, see il0'EllEJ«T, PkBCEI'TIO.N OF. The investigations of the intensive sensible dis- crimination are included under Weber's law, a proposition which may be stated thus: the ratio of the increment of stimulus, necessary to give a noticeably different sensation, to the existing stimulus is constant. The problem is, then, to discover whether this principle of the constancy of the relative difference limen is applicable to each sense department, and to ascertain the nu- merical value of tliC constant in those depart- ments in which its applicability is established. E. H. Weber himself determined the constants for pressure as follows: with simultaneous ap- plication of the weights to both hands, 1/3; with successive applications to the same hand, 1/14 to 1/30 ; with simultaneously lifted weights ( involv- ing both pressure and strain sensations) 1/15 to l/"20; with weights lifted successively with one hand, 1/40. These figures have been modified by subsequent investigators, notably G. T. Fechner, J. Merkel. and recently L. ilartin and G. E. Miil- ler (in an extended qualitative analysis of the conditions of such tests). The discriminability of temperature iiitensities varies with the jjart of the body tested, and especially, it seems, with the thickness of the epidermis. Fechner's constant is 1,8° C, E. H. Weber's 1.4° to 1.5° C. The region of finest discrimination seems to be that between 2G° and 33° C. Cooling is noted sooner than warming, in the proportion of three to two. Of taste, little is known save that Weber's law holds approximately for bitter and salt. The phenomenon of 'taste contrast' is a source of un- avoidable disturbance in this field. A careful survey of the olfactory sense has confirmed the applicability of Weber's law to smell, and es- ti'blished the constant at 1/3 with 30 per cent, of the substances tested, and at 1/4 for 26 per cent. Jlost successful results are those obtained in audition. The relative sensible discrimination for noise, tested by the fall phonometer or the sound pendulum, remains constant at 1/3 within a wide range of intensities. Technical difficulties impede the obseratinn of tones, but enough has been done to show that, at least within the central part of the scale, variations in tonal in- tensity follow the law. Work in brif/htness is subject to many sources of error — difficulties in securing standird conditions of adaptation, accom- modation, etc. The many investigations which have been completed do not. therefore, concur as to the constant, which is variouslv estimated at 1/60, 1/100, 1/120 to 1/230. The value 1/110 may be assumed as approximately correct. Of interest in this connection is the apparatus which can be employed to demonstrate the existence of the con- stancy or to indicate its numerical value. 'Mas- son's disks' are white disks, on one radius of which a number of hea^y black sections are marked. Upon rapid revolution there is pro- duced a series of concentric gray rings decreas- ing in darkness toward a periphery. The same ring remains, within certain limits, just visibly gray when the illumination is changed. liiiiLioGa-vpiiY. Ebbinghaus, (Jrundziige der I'sycholugie (Leipzig, 1897); Gamble, American Journal uf Psycholoyy, vol. x. (Worcester, 1898) ; Kiesow, I'hilosophische Htudien, vol. x. (Leipzig, 1894) ; Kueipe, Outlines of Psychology (New York, 1895) ; ilartinand Mueller, Zur Analyseder Unterschiedsempfindlichkeit ; experimentelle Bei- triige (Leipzig, 1809) ; Stumpf. Tonpsychologie, vol. i. (ib., 1883) ; Wundt, Orundziige dfr phygio- logischen I'sychologie, vol. i. (ib., 1893). See Psychology, Expekimext.vl ; Fechner; Psycho- riiY.sics; Psychological Apparatus. INTENT (Lat. intentus, purpose, from tii- tendere, to stretch, intend, from in, in + tendere, to stretch; connected with Gk. rclvew. teinein, Skt. tan, to stretch, and ultimately with Eng. thin). As emplojed in law, the purpose or de- sign with which an act is done. Ordinarily the legal consequences which flow from acts are en- tirely independent of the intent or motive with which the acts are performed. This is true of all violations of the general rights, known as rights in rem, more commonly described as prop- erty and personal rights. Thus the right to 'je free from trespass and the right to be secure from violence or from arbitrary arrest do not depend in the least on the motive or intent of the person violating them. It is only in those cases in which the rights claimed flow from the engage- ments of a party, or in which the law has. from motives of its own, attached consequences to the intent with which an act is performed, that in- tent acquires any legal significance. Obviously any rights claimed under a will, a deed, or a contract flow from the intent of the person exe- cuting it, and, in certain classes of torts, a malicious or fraudulent motive may constitute the gravamen of the offense complained of. But, in all of these cases, it is not the actual and secrL>t motive, but the expressed intent which determines the legal character of the act in ques- tion. This is the real meaning of the rule which forbids the introduction of parol evidence to con- tradict or vary the terms of a written instru- ment. The grantor of land is not permitted to show that he intended to convey another and different parcel of land. He must stand by the intent as expressed in his deed. So, in a will, a legacy to A cannot, by proof of a contrary intention on the testator's part, be converted into a gift to B, nor can one who has sold a horse for $100 show- that he intended to charge .$150 for the animal. Analogous to this principle is the rule applied in those wrongs in which intent is an element, as in malicious mischief and cer- tain cases of defamation and negligence. The person committing the injurv- is held to have in- tended the reasonable and probable consequences of his acts, and cannot exonerate himself from liability by showing that his intention was reall.v of an inntx'ent or benevolent character. There are other clas.ses of cases, however, in which the actual intent with which an act was perfonned is a proper matter for judicial in- quiry. This is especially so in cases where the wrongful intent is the gist of the wrong, as in actions for deceit, and, under certain circum- stances, in proceedings to set aside fraudulent conveyances. See Deceit: Fraidilext Con*"ey- AXCE: Interpretation: Sales: and the author- ities there referred to.