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 

 hehtninsr 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 



