532 
Frocccdwgs of the Royal Irish Academy. 
selenious acid by sulphurous acid ; and Hittorf, wliile noting the likeli- 
hood of such an influence, was unable to detect it, and was obliged to 
attribute the observed change of amorphous into crystalline selenium, 
while drying in sunlight, entirelj" to the effect of heat. In pursuing 
the line of research we have marked out for ourselves, we have been 
obliged to repeat much already published work, w^hich with improved 
means of experiment has lost somewhat of its significance. "We have 
thus encountered several apparently contradictory statements, some of 
which our experience has either failed to verify, or has placed in a 
new light ; and we have been convinced that the properties of this 
remarkable substance are but imperfectly understood, and still present 
a wide field for investigation. Vitreous selenium is, we should say at 
the outset, apparently an absolute non-conductor of electricity. "We 
have been unable to obtain any deflection of the very sensitive astatic 
needle of a high resistance galvanometer, when the thinnest films of 
selenium, of the continuity of which we could assure ourselves, are inter- 
posed in the circuit of ten Leclanche elements. The difficulty of 
producing very thin films of absolute continuity disposes us neverthe- 
less to state our belief, as to the complete non -conductivity of vitreous 
selenium with some reservation. 
As might be expected from this character, selenium in the vitreous 
form becomes electric by friction. So easily indeed have we invariably 
obtained this result that we find it difiicult to understand the contrary 
conclusion of Berzelius. 
Hittorf, as has been stated, found that when vitreous selenium is 
converted into the granular form its electrical resistance diminishes 
directly with its temperature, but that when 217° is attained the 
resistance is suddenly and largely augmented. In repeating this 
experiment we have obtained results concordant with those of Hittorf, 
who appears, however, not to have exceeded the temperature of 217°. 
Going beyond this point, we find that the resistance diminishes up to 
the point of complete fusion of the selenium, being at its maximum at 
250°. We have obtained also the remarkable result that when the 
vitreous selenium resulting from the rapid cooling of the completely fused 
granular form is quickly heated, it begins to conduct the current at a 
temperature between 165° and 175°, and that its resistance diminishes, 
not only up to the extreme range of the mercurial thermometer, but so 
much beyond that it is still diminishing when, owing to the rapid 
volatilization of the selenium, it has been found necessary to terminate 
the experiment. 
It has hitherto been assumed that there is but one granular form of 
selenium, and that this is a conductor of electricity. We have, how- 
ever, obtained a granular form in no way optically differing from 
granular selenium of comparatively low resistance, through a rod of 
which, 16m. m. long and 3m. m. diameter, the current of ten Leclanche 
cells does not in the least deflect the needle of our highly sensitive gal- 
vanometer. Nor does light, so far as our experiments have yet gone, 
diminish the resistance of this modification. We have on the other 
