214 



Tlie author observes, that many singular facts have occurred in the 

 course of his researches, some of which bear upon general science. 

 Weak solutions of salt act strongly upon copper, but strong ones do 

 not affect it, apparently because they contain little air, the oxygen of 

 which seems necessary to give the electro-positive power to these 

 menstrua ; upon the same principle, alkaline solutions and lime- 

 water prevent the action of sea-water on copper, having in them- 

 selves the positive electrical energy which renders the copper ne- 

 gative. 



The author concludes this paper with some further applications of 

 electro-chemical theory to the subject of it, and refers to the prin- 

 ciples developed, as suggesting means of preserving instruments of 

 brass and of steel, by iron and by zinc, a circumstance already taken 

 advantage of by Mr. Pepys, in inclosing delicate cutting instruments 

 in handles or cases lined with zinc. 



On the apparent Direction of Eyes in a Portrait. By William Hyde 

 Wollaston, M.D. F.R.S. and V.P. Read May 27, 1824. [Phil. 

 Trans. 1824,^.247.] 



When we consider, says the author, the precision with which we 

 commonly judge whether the eyes of another person are fixed upon 

 ourselves, it is surprising that the grounds of such judgement are not 

 distinctly known, and that most persons in attempting to explain the 

 subject would overlook some of the circumstances by which they are 

 generally guided. Though it may not be possible to demonstrate, 

 by any decisive experiment, on the eyes of living persons what 

 those circumstances are, we may find convincing arguments to prove 

 their influence, if it can be shown in the case of portraits, that the 

 same ready decision that we pronounce on the direction of the eyes 

 is founded, in great measure, on the view presented to us of parts 

 which have not been considered as assisting our judgement. 



Dr. Wollaston then adverts to the influence of the form of the 

 iris, as announcing the direction of the eye in portraits, and to that 

 of the variable portion of the white shown when the eye is variously 

 directed in living persons : he remarks, however, that even in real 

 eyes we are not guided by this circumstance alone, but are unconsci- 

 ously aided by the concurrent position of the face ; and he illustrates 

 this opinion by reference to a series of drawings annexed to the 

 paper, and which show that the apparent position of the eyes is prin- 

 cipally influenced by that of the adjacent parts of the face, especi- 

 ally those which are most prominent ; and these considerations are 

 not limited in their application merely to cases of lateral turn of the 

 eyes and face. But the same principles also apply to instances of mo- 

 derate inclination of the face upwards or downwards ; for when the 

 face is directed downwards, the eyes that look at us must be turned 

 upwards, from the position of the face to which they belong ; and if 

 to eyes so drawn an upward cast of features be substituted for the 

 former, the eyes immediately look above us, as is found by a sketch 



