Lightning Conductors in Skips. 347 



The national road crosses the Monongahela at Brownsville, sixty 

 miles (following the stream) above Pittsburgh. This village is found- 

 ed on a bed of coal, of a quality sujierior to that of Pittsburgh; the 

 precipitous banks directly opposite, present the first limestone in strata 

 which I met with, but no coal is near, nor is any limestone found on 

 the Brownsville side, unless in thin layers high above the coal. 

 From this to Washington, Penn,, the country becomes more level, 

 and the coal banks are less frequent. There we turned off the na- 

 tional road to Pittsburgh, distant twenty six miles. The banks of 

 Chartier's creek, which we crossed three or four times, are full of 

 fine coal, which is hauled six miles to supply the borough of Wash- 

 ington and its neighborhood. I have me.moranda that may enable 

 rae at a future time, to give you further particulars relative to this 

 immense coal formation and its attendant strata, but joxx must be at 

 present satisfied with this crude and hasty sketch, and a parady of 

 your remark, published in the XIX Vol. of the Journal of Science, 

 relative to the anthracite in the eastern section, " that the sun and the 

 bituminous coal of Western Pennsylvania will burn out together." 



Art. XVI. — On the Utility of fixing Lightning Conductors in Ships; 

 by W. S. Harris, Esq. Member of the Plymouth Institution. 



[From the Edinburgh New Philosophical Journal.] 



1. A THUNDER-STORM is the rcsult of a great natural action sub- 

 sisting between an extensive stratum of cloud, and a corresponding 

 portion ot the earth's surface, together with the intervening atmos- 

 phere ; and is the result of some powerful agency, the nature of 

 which is as yet undiscovered. 



2. The active principle of a thunder-storm, however, may be con- 

 sidered as an extremely subtle species of matter universally pervading 

 nature, and distributed in bodies, in quantities proportionate to their 

 capacities for it, so tiiat when accumulated in and about certain bod- 

 ies, and abstracted at the same dme from other bodies, a tendency 

 to regain the previous state of proportionate distribution is marked 

 by a certain train of phenomena ; thus, a concentrated action is fre- 

 quently set up between the overcharged and undercharged bodies, 

 which produces all the effects of a violent and terrific expansive 

 force, for the original state of proportionate distribution is often re- 

 stored by a rapid explosion, at which instant the most compact bod- 



