VOL. LXV.J PHILOSOPHICAL TRANSACTIONS. GSQ 



XXXI. Observations on the State of Population in Manchester, and other 

 adjacent Places, concluded. By Thomas Percival, M. D., F. R. S., and S. A. 

 p. 311. 



Reprinted in Dr. Percival's collected works recently, 1807, edited by his 

 son, in 4 vols. 8vo. We shall therefore only observe here, that from these 

 tables it appears, that the proportion of males to females baptized, is nearly as 

 12 to 114, or 19 to 18 ; but that the number of females living is to the number 

 of males as about 1 1 to \0\, or more exactly as 14 to 13 ; and that the widows 

 are almost double the number of widowers. 



XXXII. On the Effects of Lightning on a House, which was furnished with a 

 Pointed Conductor, at Tenterden, in Kent. In Two Letters from Richard 

 Haffenden, Esq., the Proprietor of the Hoiise, to Mr. Henley. To which 

 are added some Remarks by Mr. Henley, p. 336. 



This was an oblong house, about 50 feet long and 30 broad, having 4 stacks 

 of chimnies, 1 at each end, to one stack of which was fixed a pointed iron con- 

 ductor, projecting 5 feet above the top of the chimney. The lightning struck 

 the chimney diagonally opposite to and the farthest from that of the conductor 

 and in its passage injured several parts of the building, where the conductors 

 were imperfect or discontinued. On the account given of the house and the 

 accident, &c. Mr. Henley remarks that, 1st, A sharp pointed conductor did not 

 in this instance, invite or draw down on itself a stroke of lightning. 2dly, 

 Such a conductor, elevated 5 feet above the top of the chimnies, to a house of 

 this dimension, may not perhaps be sufficient, by its silent attractive force, to 

 protect the whole of such a building from a stroke ; especially when a chimney, 

 a blunt body, wetted with the rain, standing at 50 feet distance from the con- 

 ductor, and being within 5 feet of its height, is in actual contact with so large, 

 though irregular, a communication of metal, leading from the chimney directly 

 to the conductor ; though, in this instance, it should be remarked, that the 

 conductor itself was not in contact throughout ; and it is, for that reason, a 

 very exceptionable case. 3dly, Two such conductors ; one, for instance, on the 

 chimney where this was placed ; and the other on the chimney which was 

 stricken, with a communication of lead between them, would probably have 

 protected the house : but a conductor on each chimney would certainly have 

 secured the whole building effectually. 4thly, As the 3 branches, or divisions 

 of the lightning, all concentrated on an iron bar, three quarters of an inch 

 square, and produced no sign of heat in it, an iron bar of that size seems to 

 be fully sufficient for the purpose. There appears however to have been 2 

 defects in Mr. Haffenden's conductor : 1 . The leaden pipe and the iron bar at 

 the bottom were not in contact. 1. The iron bar, or a thick plate of lead, 



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