8i2 THE POPULAR SCIENCE MONTHLY. 



The Committee of the Meteorological Society, however, seems^very 

 soon to have lost sight of its own excellent design, and to have changed 

 its plan into a mere conference for the preparation of a report, which 

 was drawn up under its auspices and printed and published in 1882, 

 apparently by the conference itself, and which assumes the form of a 

 code of rules for the erection of lightning-conductors, with numerous 

 appendices referring to authorities which had been in some sense con- 

 sulted. The report is published under the editorship of the secretary, 

 and simply as having been considered and adopted by the delegates of 

 the conference, who seem indeed to have concentrated their attention 

 upon one subordinate object which had been proposed by the Meteoro- 

 logical Society, namely, " the diffusion of exact information regarding 

 the best form and arrangement of lightning-conductors," and to have 

 overlooked entirely the more important work of observation and record 

 which had been contemplated by the society in the first instance, and 

 to which we have drawn attention. 



The code of rules put forward by the conference was obviously in- 

 tended to possess the same kind of authority and position as the "in- 

 structions " of the earlier French reports, and indeed its chief value 

 seems to be the approval it accords to the practice of construction 

 which had grown out of those instructions, and which is very generally 

 in use at the present day. It virtually confirms most of the conclu- 

 sions which had been arrived at by the French commissions. 



The " Rules " of the London Conference direct that the main stem 

 of the conductor shall consist of a copper rod or tape, with an ascer- 

 tained electrical conductivity amounting to ninety per cent of that 

 which pure copper would possess, and weighing six ounces per foot ; 

 or that it shall be an iron rod weighing two pounds and a quarter per 

 foot ; and that the earth connection shall be made by a copper or iron 

 plate presenting a superficial area of eighteen square feet, imbedded 

 in moist earth, and surrounded with coke. The terminal points are to 

 be more prominent than those usually adopted in England, but they 

 may be less so than the heavy tiges of thirty-three feet employed in 

 France. The rod is not to be insulated from the building, but inti- 

 mately connected with all large masses of metal used incidentally 

 in the construction. All joints in its length are to be imbedded in 

 solder. Curves are not to be made too sharp, and ample provision is 

 to be secured for free expansion and contraction by varying tempera- 

 ture. Water - mains and gas-mains are to be utilized as means of 

 earth contact wherever practicable, and the conducting integrity of 

 the rod is to be tested every year. 



A careful perusal of the Frencb instructions, or of Mr. Richard An- 

 derson's very excellent manual upon lightning-conductors, published 

 in 1879, will show that this is substantially an authoritative acceptance 

 of the measures already advised by the best authorities. It is, how- 

 ever, Gomewhat remarkable that in the report itself of the London Con- 



