98 C. W. DARLEY. 



NOTES ON DAMAGE CAUSED BY LIGHTNING TO 

 SEAL ROCKS LIGHTHOUSE on 10th JULY, 1900. 



By C. W. Darley, m. Inst. c.e. 

 [With Plate II.] 



[Bead before the Royal Society of N. 8. Wales, August 8, 1900.'] 



The Seal Rocks Lighthouse which is situated one hundred and 

 seven miles north of Sydney stands on a bold projecting headland 

 at an elevation of two hundred and fifty-eight feet over sea level. 

 The lighthouse stands by itself on a well defined conical hill, the 

 keeper's quarters being built on a lower plateau, and distant about 

 three hundred feet. 



The day the lightning occurred had been fine, but for two days 

 previously heavy thunder clouds hung low over the locality, and 

 there had been frequent peals of thunder, but apparently this 

 condition was quite local, although it extended some distance 

 inland, for at Bungwall six miles, and Bullahclelah about twenty 

 miles inland> a similar atmospheric state was reported. At 3 p.m. 

 the light tower was struck by lightning. 



The tower is fitted with a solid copper lightning conductor 1J 

 in. by fin. half round, and is attached at top to the copper roof of 

 lantern. It passes down outside the lantern to the gallery, and 

 then passes in through the lantern base, and down the inside of 

 the tower, being secured to the wall with copper screws in lead 

 plugs. Upon reaching the floor of the lamp room in basement, it 

 passes out under the wall, and is then taken underground to earth, 

 but where or how has not yet been ascertained. 



The electric fluid entered the vane on top of lantern dome (the 

 ends of the feather being bent and fused and the base mold lifted 

 3 in.) thence passing down the lightning rod. A portion of the 

 ourrent was communicated to the electric bell wires on the middle 



