532 



Major J. Herschel. 



bare assertion of belief in the insecurity of the holding might fairly 

 be challenged. 



The above result could in no way be passed by. It was necessary 

 to run any needful risk to ascertain further whether the evil was 

 accidental and capable of being remedied without some decisive altera- 

 tion. I therefore loosened the fastening and drew out the wire. The 

 only result of this was to show that the wire was held solely by the 

 pinch of a split screw. This is the " special manner " alluded to in 

 the description, and I have no hesitation in saying that it is bad, 

 because it relies on the almost microscopic accuracy of cutting of the 

 parts. Assuming that no play is required in respect of length, there 

 can be no objection to doubling back the wire before clamping it — and 

 that in a large screw, split boldly for half an inch or more. ~No slip 

 could possibly happen in that case, even with very slight clamping. 

 This is the hold I have used (in the experiments alluded to), the 

 clamp being a cleft in wood, pinched ad libitum. 



Under the circumstances I replaced the wire, and screwed the hold- 

 ing nut nearly to the utmost the screw would bear ; and then repeated 

 the test — with the same result. The hold by friction (of brass upon 

 gold) is, at any rate in this particular case, insecure. Nor do I see 

 any means of remedy short of partial reconstruction, which should, 

 of course, extend also to the other five holding points. 



Should any doubt remain as to the slipping I add the following. 

 Wishing to see whether it was due to the split being too coarse, I 

 decided on extricating the holder and examining it under a micro- 

 scope ; as also to see if the wire showed any abrasion or destruction. 

 To get the holder out involves a great deal of dismemberment ; but 

 the choice lay between this and leaving the question in some doubt. 

 I succeeded in doing it — it is needless to describe how. The first result 

 was the possibility of recognising clearly the nature of the holder, of 

 which I give here an enlarged view. It is a screw about f inch long, 

 with capstan head, and three capstan nuts ; of which two hold it on 

 the beam, and the third pinches the split point. The split is quite flat- 

 sided. The shank is hollow, as far as to the end of the slit, where 

 there is a cross tunnel. By way of trial I pinched a piece of 

 silver wire in the way the suspension wire is pinched, and twisted it. 

 It was thinner than the latter. I think the pinch held it, for it soon 

 broke. This was against the theory of slipping. Fortunately, I had 

 saved a fragment of the gold wire (about \ inch) which had pro- 

 jected at the free end and had been broken off by the insertion of the 

 pin (I suppose). This piece I inserted and pinched firmly, as firmly 

 as I dared without spoiling the screw. The projecting end I bent 

 into a crook, which I grasped with tweezers. I then turned the 

 screw. Would the wire strain, or break, or slip ? That was the 

 question. The event justified previous experience. It slipped freely. 



