68 On Increasing the Rigidity of long, thin Metallic Pointers, fyc. 



close to the scale, the weight of the suspended mass is frequently 

 increased at the expense of delicacy. 



Where it is required to obtain an index or needle long, light, 

 and at the same time rigid, I suggest that the thin metal be 

 buckled : an ordinary steel pen is an example of a thin piece of 

 metal rendered very rigid by buckling in the manner proposed ; 

 but the increased rigidity bestowed by such alteration of form is 

 so well understood as to render it unnecessary to dwell on it 

 here. An index would, of course, be bent in the direction of its 

 length, and the shape of the cross section might be varied. 



It is evident that with a given weight a longer, and with a 

 given length a lighter index is possible if the metal be buckled 

 instead of used plane as at present ; a longer and finer point 

 may be bestowed on the buckled than on the unbuckled index ; 

 and the greater rigidity of the buckled index would render it pos- 

 sible to approach it nearer to the scale of the instrument without 

 fear of contact. 



I have alluded to galvanometers particularly ; but the improve- 

 ment suggested is applicable to any instrument in which a long 

 and sharp yet light index is a desideratum, while it may not 

 be required in some cases, where weight cannot be reduced by 

 reason of the necessity for a certain magnetic mass. 



I have stated the principle as applicable to indices composed 

 of metal, but it is applicable to other materials, as horn, vulca- 

 nite, &c. ; aluminium and brass, however, are probably most 

 generally applicable and would usually be employed. Slight 

 modifications in the mode of attachment might be rendered ne- 

 cessary by the buckling of the index ; but such details cannot 

 present any difficulty, while the improvement would be appre- 

 ciated by all in the habit of using instruments with long, light 

 indices as at present constructed. I have seen clock-hands in 

 which the principle has been partially applied ; but in such cases 

 it is scarcely necessary, and ornament appears to be generally 

 the object. The subject of this paper suggested itself to me 

 from the difficulty I have found in keeping the needles of de- 

 tectors &c. flat in spite of the handling of them in remagne- 

 tizing, and in using delicate galvanometers, the long light 

 needles and long thin brass pointers of which have to be occa- 

 sionally handled, are very readily bent, and by no means readily 

 rendered straight again. 



