•166 On the Electric Column of Mr. De Luc. 



in 1814. I think you got it from me, stated to have Isen put 

 up in the year 1641, as is Mr. Grignion's account of it. 

 I am, sir. 



Your most obedient servant, 

 Edinburgh, June 20, 1815. Thomas Rpid. 



LXXXIl. On the Electric Column of Mr. De Luc. 



To Mr. Tilloch. 



Sir, — OiNCE you did me the favour of inserting in your valua- 

 ble Magazine a description of my contrivance for applying clock- 

 work to Mr. De Luc's electric column, for tiie purpose of ob- 

 serving wth greater facility and convenience its meteorological 

 pii:?'nomena, and for attempting to procure by its means a mea- 

 surement of time*, 1 have had the high honour and gratifica- 

 tion of a short correspondence with the very respectaljle and able 

 inventor, on tlie title of that description which I so carelessly 

 omitted to affix, and which vou were so obliging as to supply. 

 1 sincerely thank you, sir, for having so done, and iiave no doubt 



that 



* In your last number, JNTr. Sinoer asserts that a " ^Ir. Lightfoot first 

 suggested the einploynient of an inflexible penfluliim as a merms of con- 

 verting the reciprocating motion usually produced hy the column into a 

 source of rotary movement; and tiie corrcctncfs of this idea ■(>as soon af- 

 ttrwards practically verified hy me,"' (whom he chooses to dc&icnute by the 

 apjiellation ot !>is pupil) " with, the assistance of a watch-maker." 



lie also observes, that " tlie rotary motion obtained by this indirect 

 means ij however rather ciirions than useful, for it is scarce!)/ so correct an 

 indication of the power of the column as the simple pendulum, iS:c." J do 

 not notice tlie first remark, for tiie purpose of claiming either for myself or 

 for Mr. Goriiam the watch-mak«r any merit in so simple a contrivance, 

 but to protest against tlie ambiguous con.«truction of the paragraph, by 

 which, if lie does nut mean it, he appears desirous of having !t understoofi, 

 that I eitlier directly or indirectly derived the idea from the suggestion of 

 Mr. Li^htfoot, and thus appears to in^inuate plagiarism. Mow, even if 

 1 thought he did mean to make this insinuation, I would not trouble either 

 yuu or him with its confutation. 



I notice the Second remark, only for the purpose of observing that his 

 instruction would m this case lead those into error who might be induced 

 to avail themselves of the advantages which I derive in using the clock- 

 work, since 1 have found, bv having for some time past, and under a great 

 variety of circumstances, carefully compareil it with ail the other modifi- 

 cations he describes, that it is not scarcelt/ hut perfectly as correct an indi- 

 cation of the power of the colunui as any one of those modifications. I 

 sus[)ect that the " considerable irregularity" observable in the motion of a 

 pith-bal! suspended b" a silk thread, is not occasioned wholly by the varia- 

 tion of the temperature of the surrounding medium, and the state of mois- 

 ture, &c. but partly by a tcideucy to stick to the halls against which it 

 ilrikes, and will one day cause it to stop. To avoid this inconvenience, I first 



attached 



