309 
however, of this mineral received from Professor Jellett occur- 
ring in six-sided prisms, which appeared to have the property 
of depolarizing a ray of light transmitted along the prismatic 
axis, it was inferred that they were biaxal, and, therefore, be- 
longed to the right prismatic system. This opinion, how- 
ever, had to be abandoned, as the double system of rings 
characteristic of biaxal crystals could not be developed, so 
that the depolarizing power of these crystals in the direction 
of the optic axis must be attributed to laminar polarization, or 
to the same cause which is known to communicate double re- 
fractive properties to analcime and certain other crystals in 
the regular system. 
Dr. Petrie exhibited some Irish antiquities lately obtained 
by Mr. Kelly, of Armagh. 
Dr. Apjohn exhibited a portion of bell-wire melted by 
lightning on the 3rd of June last, in the house of Richard Pen- 
nefather Lloyd, Esq., 19, Herbert-place. 
The lightning struck the chimney of the adjacent house, 
No. 18, where it dislocated the bricks immediately under one 
of the chimney pots. From this it passed to the gutter run- 
ning between the back and front roofs of Mr. Lloyd’s house, 
and entered the attic story by a spark, between a holdfast 
supporting the gutter and the bell-wire within, making a 
small perforation in the wall. At this point the wire was 
fused, and in two other places, namely, at the level of the 
bed-rooms underneath, and in the vicinity of the drawing-room 
door. Its further progress could not be traced, and the only 
visible effects of its traject were the destruction of the bell- 
wire and an irregular blackening of the wall at the points at 
which the fusion took place, a result which was probably due 
to the charring of the paint by the heat of the spark which 
must have occurred wherever the continuity of the conductor 
along which the lightning was passing was destroyed. No 
