130 Lightning connected with Glass and Metals. 



perpendicular line let fall from the extremity of its longest 

 branches. 



Influenced by the consideration of certain analogies, natural 

 philosophers generally admit that lightning always respects 

 glass. Starting from this postulate, there is only a single step 

 to the conclusion that a chamber wholly constructed of glass 

 would be a perfectly secure refuge. Hence chambers or cases 

 have been proposed, and actually constructed for the use of 

 those who are apt to be overwhelmed with panic during a thun- 

 der storm. Though unquestionably disposed to grant that 

 under the circumstances an envelope made of glass may some- 

 what diminish the apprehended danger, yet I cannot admit 

 that it wholly removes it. And my reasons are these. The 

 great thunder-storm which injured the palace of Minuzzi, in 

 the territory of Ceneda on the 15th of June 1776, pierced or 

 h?vJi:e more than 800 panes of glass. Again, when Mr James 

 Adair was prostrated, in September 1780, by a violent stroke 

 of lightning, which killed two of his servants in his house at 

 Eastbourne, he was standing behind a glass window. On that 

 occasion the window-case was not at all injured, whilst all the 

 glass had completely disappeared, the lightning having reduced 

 it to powder. 



Some, perhaps, may conclude that the rupture of glass on 

 guch occasions as these is the consequence of the violent con- 

 cussion of the air — a simple effect of the noise and detonation. 

 There are not, however, wanting facts which set aside this hy- 

 pothesis. On the 17th of September 17752 the lightning which 

 fell at Padua on a house in the Prato della Valle, pierced a 

 pane in a window on the ground-floor with a clean and rotmd 

 hole^ precisely such as a gimlet would make in a board. Again, 

 Caseli, the engineer of Alexandria, observed upon the glass of 

 his windows immediately after a flash of lightning, in the year 

 1778, a number of small round apertures with scarcely any ad- 

 jacent fissures. Once more, in September 1824, a thunder-bolt 

 having fallen on the house of Mr Wm. Brenmer at Milton 

 Comage, one of the panes of the window was found pierced by 

 a circidar hole of the size of a musTcet hall ; in the other parts 

 of the pane there was not a single crack or fissure. A perfectly 

 circular hole of this sort without fissures, cannot be the conse- 



