Septembee 21, 1906.] 



SCIENCE. 



375 



letter from the Philosophical Transactions, 

 in No. 11 of Neudruclce von Schriften und 

 Karten iiber Meteorologie und Erdmag- 

 netismus (Berlin, 1898), that an important 

 omission had been made in the slightly dif- 

 ferent version printed in the collected papers. 

 The present writer finds that this error has 

 been perpetuated by such careful biographers 

 of Franklin as Sparks, Bigelow and Smyth, 

 who, having reprinted the letter from the col- 

 lected papers, also omit this concluding para- 

 graph : 



I was pleased to hear of the success of my ex- 

 periments in France, and that they there begin to 

 erect points upon their buildings. We had be- 

 fore placed them upon our academy and state- 

 house spires. 



Professor Hellmann supposes that Frank- 

 lin, by the last statement, wished to claim 

 priority in the use of pointed rods as light- 

 ning conductors. 



Already in his ' Opinions and Conjectures 

 Concerning the Properties and Effects of the 

 Electrical Matters, arising from Experiments 

 and Observations made at Philadelphia, 1749,' 

 contained in a letter to Peter Collinson, dated 

 Jtily 29, 1750, Franklin had proposed to test 

 the electricity of thunder-clouds and had sug- 

 gested the possibility of the lightning-rod. In 

 order to continue his experiments, Franklin, 

 in September, 1752, erected on his house an 

 insulated iron rod, connected at its lower end 

 with a pair of bells which, by ringing, would 

 show that the rod was electrified. On April 

 17, 1753, he charged one Leyden jar from this 

 rod and another jar with positive electricity 

 from a frictional machine, concluding from 

 this and subsequent experiments 



That the clouds of a thunder-gust are most 

 commonly in a negative state of electricity, but 

 sometimes in a positive state. 



Further on in the same letter in which the 

 preceding experiments were described, written 

 at Philadelphia in September, 1753, Franklin 

 says : 



Metalline rods, therefore, of sufficient thickness, 

 and extending from the highest part of an edifice 

 to the ground, being of the best material and 

 complete conductors, will, I think, secure the 

 building from damage, either by restoring the 



equilibrium so fast as to prevent a stroke, or 

 by conducting it in the substance of the rod so 

 far as the rod goes so that there shall be no 

 explosion but what is above its point, between 

 that and the clouds. 



f his is generally believed to be the first 

 definite announcement of the lightning-rod, 

 although Poggendorff, in his ' Geschichte der 

 Physik,' page 867, casts doubt on Franklin's 

 sole claim to its invention by saying that 

 J. H. Winkler, of Leipzig, in his ' Programma 

 de avertendi fulminis artificio,' Lipsia, 1753, 

 recommended the use of lightning conductors 

 and gave directions for their erection, in con- 

 sequence of which, probably, they were first 

 introduced into Germany in 1754. 



I shall show, however, by what follows that 

 Franklin had prepared detailed instructions 

 for the installation of lightning-rods nearly a 

 year before he wrote the letter that has just 

 been quoted. In Poor Richard's (Improved) 

 Almanac for 1753, edited by Richard Saun- 

 ders (Benjamin Franklin's pseudonym) and 

 published in Philadelphia by B. Franklin and 

 D. Hall, the material for which must have 

 been ready not later than October, 1752, oc- 

 curs the following remarkable article which 

 seems to have entirely escaped the attention 

 of Franldin's biographers and of scientific stu- 

 dents generally. 



Hoio to secure Houses, &c. from Lightning. 

 It has pleased God in His Goodness to Mankind, 

 at length to discover to them the Means of se- 

 curing their Habitations and other Buildings 

 from Mischief by .Thunder and Lightning. The 

 Method is this: Provide a small Iron Rod (it may 

 be made of the Rod-iron used by the Nailers) but 

 of such a Length, that one End being three or 

 four Feet in the moist Ground the other may 

 be six or eight Feet above the highest Part of the 

 Building. To the upper End of the Rod fasten 

 about a Foot of Brass Wire, the size of a common 

 Knitting-needle, sharpened to a fine Point; the 

 Rod may be secured to the House by a few small 

 Staples. If the House or Barn be long, there 

 may be a Rod and Point at each End, and a 

 middling Wire along the Ridge from one to the 

 other. A House thus furnished will not be dam- 

 aged by Lightning, it being attracted by the 

 Points and passing thro the Metal into the 

 Ground without hurting any Thing. Vessels also. 



