514 



SCIENCE 



[N. S. Vol. XL. No. 1032 



The dome which had just been completed 

 was barely out of sight from where I stood and 

 no one at the observatory seems to have seen 

 the actual flash. A peon however in the 

 grounds of the Meteorological office about 100 

 meters away had a full view of both domes and 

 buildings, was facing them and saw the flash 

 just over and about the new dome. This ac- 

 cords well with the direction and distance from 

 my point of observation. 



After hearing of this observation I made a 

 careful examination of the dome and in par- 

 ticular the connection of the copper cable with 

 the track upon which the dome revolves, which 

 forms the connection between the metal dome 

 and one of the vertical I beams imbedded in 

 the concrete for grounding the circuit. The 

 lightning-rod proper extends about a meter 

 above the highest part of the dome and termi- 

 nates in a brush of heavy wire. No signs what- 

 ever of any discharge have been found at any 

 point about the dome. 



Close to the dome stands the wooden derrick 

 which was used in its construction, the top of 

 which is about two feet higher above the 

 ground than the lightning-rod. Three wire 

 cable guys lead ofE to trees, two of which actu- 

 ally touch the ground — but scarcely so — and a 

 fourth to a brick building. The cable used for 

 lifting did not touch the ground. Careful ex- 

 amination of all of these points failed also to 

 disclose the slightest sign of a spark. 



The three wires of the alternating power 

 circuit pass close to both dome and derrick. 



About 70 or 80 meters east and west are, re- 

 spectively, three lightning rods on the direc- 

 tor's residence, and one on the assistants' 

 house. To the south some 100 and 150 meters, 

 respectively, are the metallic tower for the 

 windmill and water tank, about 50 feet high 

 and the first astronomer's residence with two 

 lightning points. 



I have been particular in referring to these 

 various conductors, for it seems probable that 

 so many must have been instrumental in re- 

 ducing the difference of potential somewhat. 



The bolt which struck the dome was un- 

 doubtedly not a light one for it frightened 

 badly a number of persons in the residences 



near by and was described by several as a very 

 bright flash. I do not think, however, that it 

 was an especially heavy one, possibly not so 

 heavy as most of the others which struck in 

 the vicinity. 



The peon who saw it from the neighboring 

 quinta, was seated at the time under a shed and 

 watching the dome. He says the flash ap- 

 peared to descend as a single ray, striking the 

 lightning rod and then the whole surface of 

 the metallic dome appeared to be covered with 

 sparks or flashes. 



At the time the bolt struck there was a peon 

 inside the closed dome, cleaning the running- 

 gear. When questioned he said he had felt 

 nothing nor had he noticed anything unusual 

 beyond the heavy noise. 



It seems certain, therefore, that the dome 

 was actually the principal point of discharge 

 for a fairly heavy flash of lightning. (It is 

 uncertain how much of the discharge was 

 taken by the derrick, but it would appear to 

 have been relatively small.) That the in- 

 duced currents in the light and power lines 

 were sufficiently heavy to blow the fuses in 

 both. 



This experience seems to be a fairly severe 

 test for such a construction — a metallic dome 

 surmounting concrete walls which are heavily 

 reinforced with iron — the metal in the walls 

 having a good ground connection and being 

 connected also with the dome. 



From the effects in this ease one concludes 

 that after the resistance of the air was broken 

 down, the dome and metal in the walls were 

 ample to carry off the discharge without the 

 slightest apparent damage to either the struc- 

 ture or the man who was inside at the time. 



CD. Pehrine 



Observatoeio Nacional Aegentino, 



C6RD0BA 



SCIENTIFIC NOTES AND NEWS 



An international committee has been 

 formed to establish a foundation in memory 

 of Henry Poincare. A medal will be struck 

 in his honor, and a fund will be established 

 under the Paris Academy of Sciences to en- 



