300 



ADVANTAGES OF A LARGE KNIFE IN MAKING PENS. 



XIV. 



On Gridiron Pendulum Bods compofed of Lead and Iron, By 

 Mr, Blnzenberg *. 



Mr. B. employs iVlR. B. was induced to employ lead on account of its great 

 lead, on^^account ^jj^jj^j^jUj^^^ ^j^j^j^ -^ ^^ j^.^^^ ^^ 2.57 to 1, fo that 16.5 inches 



tabUity. of lead compenfate 1.3 of iron; and he chofe iron in prefer- 



Hls compenfa- cnce to fteel, becaufe eafier to work. The corapenfation was 

 tion made by a made by a fingle rod in the centre, \6\ inches long, French 

 •mchesby |an*nieafure, and f an inch thick. It was fimply pinned into 

 inch. gorges in the crofs-piece of copper ; but the other parts of the 



gridiron were rivetted in the ufual way. The iron rods were 



made of the beft thick iron wire. 

 Its advantages. The materials of thi? pendulum are cheap, and it may be 



made in a couple of days. As the prelTure takes place in a 



vertical diredion, there is no danger, according to Mr. B. of 



rodsof thefedimenfions bending. 

 Mode of cor reft- To correft the compenfation, the central rod of lead mufl 

 ing the compen- j^g |gf^ fQ j^j^g ^^^t we may be fure the compenfation is in ex- 



cefs. The quantity of error may then be found by the freezing 



apparatus, and how much it is requifite to cut from the rod may 



be calculated with the greateft exaftnefs. 



XV. 



On the Advantages of a large Knife in making Pens. By a Cor- 

 refpondent. 



To Mr. NICHOLSON. 

 SIR, 



The edge of a UsEFUL difcoveries are fomelimes derived from the com- 



large knife is j^q^ occurrences of life ; and that which I am now going to 



©rrfoJall one.^ mention, is a mere accident of this kind. About three years 



ago, I took up a large pocket knife which had been newly 



ground, and ufed it for making a pen, and was not a little 



furprized to find that it anfwered the purpofe much better than 



* Foigfs Magazin fuex den ne'vejlen Zuflande de Naturhunde, 

 Vol. IV. p. 787. 

 ; c any 



