117 
The substance to which these statements refer is the transparent sul- 
phuret of arsenic; this substance is selected because the experimental 
results of Jamin, and the values given by Fresnel, differ more widely 
for this substance than for any other. It furnishes, therefore, the best 
test of any new theory. 
Mr. Jellett stated that he had obtained for the new constant, which 
M. Jamin calls “ coefficient of ellipticity,” a value sensibly different 
from that given by M. Jamin. The value of this constant given by M. 
Jamin for sulphuret of arsenic is 
0:0791, 
while that obtained by Mr. Jellett is 
0:0914. 
The Rey. Samuel Haughton made some remarks on Mr. Jellett’s 
paper. 
Lorp Tarsot pE Matautns, on the part of T. A. Wiss, M. D., pre- 
sented a cast of a stone cross which had been discovered in Perthshire. 
Dr. Wise in the accompanying paper describes this sepulchral cross, 
recently discovered, and similar in character to a numerous class of 
crosses well known to Scotch antiquaries. 
They are well described and portrayed in two fine works, ‘The 
Ancient Sculptured Monuments of Angus,” by the late Mr. Chalmers 
of Auldbar, and ‘‘ The Sculptured Stones of Scotland,’’ published by 
the Spalding Club, through Mr. John Stuart, the able Secretary of the 
Antiquaries of Scotland. 
These crosses are, with few exceptions, confined to the part of Scot- 
land north of the Forth, but range through the eastern counties as far 
as Caithness, and even to Shetland. They are most numerous in the 
districts formerly occupied by the kingdom of the Picts. 
With considerable resemblances to the Irish crosses, they differ in 
many important respects. They contain, frequently, hunting scenes 
and very strange animals, such as bears, lions, elephants, centaurs, &c. 
There are numerous emblems, such as the mirror and spectacle orna- 
ment described by Dr. Wise, and also many others which are hitherto 
unexplained. As ageneral rule, they have no inscriptions. Almost the 
only exceptions are the stone at Newton, on the Garioch, which has a 
‘Runic or Ogham inscription, and also another in an unknown character ; 
there is also an inscribed stone at Brechin, and there is a stone at 
Bressay, in Shetland, with an inscription in Runes. A cast of this was 
exhibited at the Newcastle Meeting of the Archeological Institute ; and 
it is very much to be desired that Professor Graves, who has done so 
much in this field of research, would give his interpretation of it. 
There is another kind of crosses which are not included in those 
publications, found at Iona, and other parts of the west of Scotland. 
They are of a Scandinavian character. 
ae 
