299 
It is formed on the principle suggested by Gauss, of separat- 
ing the needle altogether from the circle by which its position 
is determined ; the moveable arms of the divided circle being 
furnished with compound microscopes, by means of which the 
extremities of the needle are observed. The circle is divided 
to 10’; and the readings are made to single minutes by the 
help of verniers. 
By a simple modification in the construction of the in- 
strument, it is capable of being used with needles of various 
lengths, not exceeding the diameter of the measuring circle ; 
and it is hoped that it will thus serve to determine the ques- 
tion, not yet solved, as to the most advantageous dimensions 
of the dip needle. 
Another, and more important, peculiarity in this instru- 
ment, is its adaptation to the determination of the intensity in 
absolute measure. In the received method, the horizontal 
component of the intensity is determined by a double observa- 
tion, and the total intensity thence inferred by multiplying it 
by the secant of the inclination. Hence, in the high mag- 
netic latitudes, where the inclination is considerable, any error 
in it will induce a large error in the inferred intensity ; and 
in the neighbourhood of the magnetic pole the method fails 
altogether. The present instrument is adapted to measure the 
4 ‘total intensity directly ; and it is easily shewn that the result 
7 ‘thus obtained is, in the high magnetic latitudes, much more > 
accurate than that deduced in the ordinary way. The instru- 
‘ment may be employed, also, for the measurement of the hori- 
‘zontal and of the vertical components of the intensity. 
1 oe in the Museum of the Academy. 
Lo Mr. Clibborn stated that he had lately detected iron 
3 _ cores in the centre of the bronze composing the mouth- 
af pieces of several ancient horse-bits in the Museum. T he 
fact was interesting, as it appeared to prove that, at the time 
Mr. Clibborn read a notice of certain Bronze Antiquities 
