44/ 



Erratum in the article on ec Lightning Conductors" published in 

 the last Journal, 



It gives me regret to have to point out a serious error in my account 

 of the accident by lightning which occurred to Dr. Goodeve's house, 

 in May, 1837. The distance of the part struck from Mr. Trower's con- 

 ductor, is twenty-two yards, instead of twenty feet, as stated in my letter. 



The error was occasioned by my entrusting the measurement to a 

 native assistant, who no doubt either contented himself by a guess, or 

 unknowingly used the word/<?e£ instead of yards in his report. Illness 

 prevented my making the measurement myself. Fortunately, however, 

 the error does not in the least degree vitiate the argument, in which the 

 accident was mentioned for illustration's sake alone. That the best conductor 

 will not protect a radius of 60 feet (as Biot has assumed it would) is now 

 proved by the history of so many lightning explosions, that an error in 

 one is of no importance whatever. The reader will find in paras. 10, 11, 

 12, 13, and 14, of my second report, sufficient facts to set this question at 

 rest for ever. 



My chief object in noticing the accident to Dr. Goodeve's house was to 

 shew, that one and the same explosion may fall on a conductor and also 

 on other adjacent bodies; that is, that one conductor may not be capable 

 of carrying off the whole of the electricity of a single flash, although the 

 conductor remain unmelted, or even be not perceptibly altered by the heat 

 of the discharge. This view is but strengthened by the occurrence as it 

 now stands in the corrected account. The greater the distance, the more 

 remarkable is it that the primary flash should have been subdivided, as in 

 this instance. Let it be remembered that Dr. Goodeve saw the flash 

 strike both objects at the same instant. 



I congratulate Mr. Daniell on the occasion thus afforded to him for a 

 further display of the peculiar tone, and temper, which characterized his first 

 report. But I repeat here distinctly, that the error into which I have been 

 betrayed does not in the slightest degree affect the inferences which all the 

 facts recorded manifestly lead to — 1st, that a conductor, however well con- 

 structed does not infallibly protect a space of sixty feet radius, — 2d, that a 

 flash of lightning may strike a conductor, and other adjacent objects at the 

 same instant. The occurrence at Dr. Goodeve's house has nothing to do 

 with the discussion regarding the " lateral discharge ;" and had the accident 

 never taken place, the arguments I advance would not be in the least de- 

 gree affected. One good result, at all events, will proceed from this 

 mistake — that I shall never again depend on the measurements made by 

 persons who do not understand the object in view, and the necessity for 

 care in their performance of so simple a task. 



W. B. O'SHAUGHNESSY. 



Calcutta, 10th September, 1840. 





