X/A' \\-ll.UAM SIEMENS, F.R.S. 129 



but the station should also be protected, and that was the case on 

 all continental lines he had been connected with, where lightning 

 . The form of lightning discharger was perhaps a 

 open to controversy, but from all he had seen of lightning 

 dischargers those with a great many points seemed to him to be 

 the safest guard against accidents to the instruments. One pair 

 of points in a vacuum was a very good protector, but it could not 

 be relied upon permanently, inasmuch as a single discharge would 

 destroy the points, and the discharger under these circumstances 

 was worse than useless. The plate protector was devised by his 

 brother many years ago. Although it seemed an arrangement of 

 two plates opposite each other, it was really an arrangement of 

 many points opposed to each other, at very short distances apart, 

 inasmuch as the surfaces were planed in opposite directions at 

 right angles with each other, forming a series of thousands of 

 points, and if by the discharge s^me of the points were burned 

 away, there were always plenty remaining to do the work. It was 

 necessary that care should be taken to clean these surfaces very 

 frequently, and there was no reason why this should not be done 

 as part of the duty of the office. The vacuum and many pointed 

 dischargers seemed to him to be the best protectors. 



"ON IROX TELEGRAPH POLES," 

 BY MR. C. W. SIEMENS, F.R.S., D.C.L.* 



THE construction of an iron telegraph pole has occupied my 

 attention for many years. The object was to combine lightness 

 and convenience of construction with the attainment of a maximum 

 of strength and resisting power to sudden jerks, and to oxidation. 

 This consideration led me to abandon the ordinary mode of fasten- 

 ing poles by setting considerable lengths of them underground, and 

 to the adoption in its stead of a buckled wrought iron plate, which 

 combines very great rigidity with a certain toughness, enabling it 

 to yield to sudden and excessive strains. 



* Excerpt Journal of the Society of Telegraph Engineers, Vol. II., 1873-74, 

 pp. 49-51, 65-70 and 79. 



VOL. II. K 



