Dr Graves on tJie Sense of Touch, 67 



Declination and Inclination of the Magnetic Needle at 

 Paris.— On the 9th November 1835, at Ih 8' p. m. we found 

 that the northern extremity of the magnetic needle pointed to 

 the west of the astronomical north, 22° 4'. On the 3d July 

 1835, at 9^. morning the inclination, was 6T 24'. 



Obsertations on the Sense of Touch, including an Analysis of 

 Weber's Works on that subject. * By Dr Graves of Dublin.-f 



Weber's experiments on the sense of Touch are extremely in- 

 teresting and original ; some of them have been already published 

 in English periodicals, but in so imperfect a manner as to fur- 

 nish a very inaccurate and incomplete view of their results. If 

 we touch the skin with the points of a compass one inch asun- 

 der, while the person so touched shuts his eyes, he at once per- 

 ceives his skin to be touched in two places. By continually di- 

 minishing the distance between the two points, we finally arrive 

 at a degree of approximation where the person feels his skin to 

 be touched by but one body ; he describes this body, however, 

 as being a little longer in one direction than another, and it 

 appears that this longer diameter corresponds with the line of 

 junction between the two points of the compass. When these 

 points are brought still nearer together, this inequality in the 

 diameters is no longer felt, and the person has a defined percep- 

 tion of being touched by but one body. Now Weber has deter- 

 mined, by experiment, that the different portions of the surface 

 of the body vary considerably in accuracy of touch, as measured 

 by the distance at zohich the points of the coinpass can be still 

 distinguished from each other ; for it is evident that parts en- 

 dowed with great power of touch, will continue to give notice of 

 two points at a distance from each other, so small, that when 

 examined at the same distance by less sensible portions of the 



* De Puhu, Respiratione Audita et Tactu, AnnoioHones Anatomicae et Physio* 

 hfficae. Auctore Henrico Ernesto Weber. Lipsiaef 1834. 



t This interesting Memoir appeared in the March number of the Dublin 

 Medical Journal, which did not reach Edinburgli until a month after its 

 Usual time. 



£2 



