Lightning Conductors to Powder Magazines. 499 



may appear to affect the action of the conductors, should be 

 recorded. 



3. Details of the effects of the Discharge. 

 Under this head should be included all the consequences 

 of the discharge, and every effect which can be traced to it 

 should be recorded and substantiated. 



4. Determination of the course of the Lightning. 

 On this point mere ocular testimony must be received 

 with the utmost caution, and the true course of the dis- 

 charge from the moment of its original impact on the 

 building to that of its quitting it, can only be indisputably 

 established by its effects detailed in the preceding section. 

 By these, whether they have been due to the intense heat or 

 disruptive force which almost invariably accompany dis- 

 charges of lightning, the course of the fluid will be indicated, 

 and much care ought to be taken to trace its various steps. 

 Sometimes the discharge becomes subdivided, and follows 

 different lines; the determining causes of such separations 

 should if possible be established. The vicinity of metal to 

 the original point of impact, and its relations to the course 

 pursued by the lightning, should be most carefully noted. 

 All the information obtained relative to the course of the 

 lightning should be laid down on the plan previously allu- 

 ded to, but prior to doing so the observer ought to scrutinize 

 most rigidly every point brought under his notice, estimating 

 the value of the statements he has received, verifying them 

 where they can admit of verification, and whenever doubts 

 are excited in his own mind on any point, they should be 

 openly and fully expressed by him. 



5. Meteorological and General Observations. 

 The state of the Barometer, Thermometer, Hygrometer, 

 and such other meteorological instruments as the observer 

 may have access to should be carefully noted, and also the 



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