No. 2. 



X 



Protection from Lightning. 



Gl 



make the necessary survey of the premises, 

 and to superintend the work. He has made 

 arrangements also to liave the machine con- 

 structed at the establishment of Mr. Winans, 

 in Baltimore, at much less than it cost me 

 to import mine. 



I would omit an act of justice, were I not 

 to mention here, that Mr. Winans has made 

 a very admirable improvement, wliich en- 

 ables the machine to be used wlicre the 

 supply of water is irregular, witliout the 

 trouble of going to it to start it after the 

 head has accumulated, and which promises 

 also to make it useful upon the largest scale, 

 even to the supply of cities, in place of the 

 water-wheel and forcing pump. 

 Respectfully, 



John H. B. Latrobe. 



Fairy Knowe, Aug. 2iid, 1)^44. 



From the North American. 

 Protectidi from Lightning. 



Within the last few years, this subject 

 has acquired renewed interest, in conse- 

 quence of the immense loss of liie and pro- 

 perty which has been sustained throughout 

 our country, by this terrific agency. It has, 

 therefore, become a practical question of 

 vast importance, in which we all have a 

 deep concern as to the causes of this de- 

 struction, and the best means of counteract- 

 ing an element so universally diftused 

 throughout space, and which left to itself, 

 proves so highly destructive. To a superfi- 

 cial observer, it must iie very manifest that 

 there exists a culpable ignorance on the 

 part of the community, in reference to this 

 whole subject, as well as a general neglect 

 in the employment of those means which, 

 both experience and philosophy have proved 

 adequate for the perfect protection of pro- 

 perty, and consequently of human life. 

 From recent investigations, it has been sat- 

 isfactorily ascertained, that the simple rod 

 of Franklin is all sufficient, if properly made 

 and applied, to secure this requisite protec- 

 tion, and that in all cases, where buildings 

 have been destroyed or much injured, it has 

 't«en owing either to a neglect of its use, or 

 to some violation of established principles 

 in itb^onstruction or application. 



No i^nkling can be considered secure 

 without a rrood conductor, and nine-tenths 

 of those nov jjgyijjfj them, are not much 

 better off, own., ^^ \jjg fVjgj. ^f ^jj^jj. ^^^^,1^^ 

 construction, tlit inadequate height and 

 termination, and thc„g|.^, nooligent manner 

 of their application. \^ ^jje nonductin^r 

 power of the rod is grt^iy influb^^^ed bv 

 extraneous circumstances, i-,hould be i..,de 

 not only with great care, bu. i^ strict tx^! 



cordance with those principles which expe- 

 rience has proved necessary, in order to 

 attain the highest possible degree of this 

 essential requisite. 



The Conductor should be made either of 

 copper or iron : — the first is by far the best, 

 as it is not liable to rust, and possesses eight 

 times the conducting power of the latter ; 

 but its very high price operates to exclude 

 it from general use, and causes iron to be 

 preferred, as its moderate cost brings it within 

 the means of every citizen and farmer 

 throughout our city and country. 



The Conductor should be of a rounded 

 form — three-quarters to one inch in diame- 

 ter — the l,arger, the better security, as the 

 conducting poioer is in proportion to the 

 solid mass ; it should be continuous, the bars 

 of which it is composed being well screwed 

 into each other, or nicely adapted, by means 

 of a mortice and tenon joint pinned firmly 

 together, by which the surfaces are brought 

 into the most intimate contact. 



The Conductor should be terminated at 

 its superior or upper end, by a stem of cop- 

 per, capped either with one or more points 

 made of gold, platina, or silver, but of these, 

 the first is the best, as its conducting power 

 is much greater than either of the other 

 metals, and if made solid, or well galvan- 

 ized, is less liable to rust, a common result 

 in a climate so moist and variable as ours. 

 In addition to this, the rod should be well 

 painted with several coats of black paint, 

 which not only protects it from the moist- 

 ure, but also tends to increase its conducting 

 power. 



As to the application. The efficiency of 

 a conductor is greatly increased by its height 

 above the building, and in this particular 

 the greatest possible ignorance prevails, not 

 only in the community at large, but in those 

 who profess to understand this subject, and 

 to furnish the necessary means of protection 

 to others. 



It is a common occurrence all over the 

 land, to see large barns and public buildings 

 of great dimensions, say of thirty, forty-five, 

 or sixty feet in extent, protected with a 

 small rod, elevated two or three feet above 

 the chimney or ridge of the roof, an experi- 

 ment not only dangerous in itself considered, 

 but a useless expense, without securing in 

 any way, the object forvvhich it was applied. 



The established rule then is. That a con- 

 ductor will protect a space every way, only 

 twice the extent of its height above the 

 building, and this rule should never be vio- 

 lated in the adaptation of the Conductor; 

 for if it is placed only three feel above the 

 ridge of the roof of a house or barn, say 

 thirty feet in length, it follows of course, 



