124 Scientific Proceedings, Royul Dublin Society. 
siliceous fire-bricks was employed, and the basic bricks were 
piled on the floor in direct contact with this lining. An intense 
white heat having been obtained, it was observed that the pile 
or stack of basic bricks had subsided, and on the oven being 
broken down after cooling, it was found that the lower layers of 
the pile had actually passed through the flooring, and that the 
siliceous bricks exhibited sharply cut moulds of the angles of the 
basic bricks where they had cut down through them. 
The resultant fused mass occurred partly in a stalactitic form 
with a minutely crystalline structure, and partly as an assemblage 
of semi-transparent crystals. 
With the permission of Mr. Gilchrist we propose to describe 
this adventitious result of his experiments. 
The crystallized mineral occurs in long prisms, apparently 
belonging to the monoclinic system. Some of the crystals were 
nearly colourless or grayish, while others were more or less 
strongly tinged with green. The hardness was slightly greater 
than 5, and the specific gravity proved to be = 2:934. 
Some of the best crystals were picked out, and afforded the 
following results on analysis :— 
Silica, . a ‘ : 5 ; 55°35 
Lime (CaQ), 3 a ; ; 2 23:24 
Magnesia (MgO), . . : ; 16:20 
Alumina and Ferrie Oxide 5 : : 4:20 
Water, loss, &., . : : : : 1:01 
100-00 
The alumina and iron are so evidently accidental constituents 
that their weights may be excluded from consideration in 
deducing the formula for this mineral. Neglecting these chance 
constituents then, we obtain the following formula on discussing 
the analytical data in the usual way :-— 
MgSiO, + CaSiO, 
Or, its formula may be written, 
( Mg + 3 Ca) SiO,. 
The mineral is therefore a Bisilicate, and is a true Pyroxene. 
Its composition indicates that it is a member of the group 
of Pyroxenes that includes Malacolite and Diopside. Messrs, 
Thomas and Gilchrist have therefore effected, accidentally, and 
under novel conditions, the synthesis of an interesting member of 
a most important group of minerals of natural occurrence. 
