55 
H ' V 
Description of Achmite, a New Mineral. 
supported on a long point of brass or steel in a compass 
bowl, from which is suspended a rhomboidal compass-needle. 
On the center of the brass cross there is a light case of card 
paper fitted to the pocket chronometer to be carried by it. 
The case for the chronometer slips upon two pins rivetted to a 
moveable plate upon the cross, which being made to slide in dif- 
ferent directions, may be so placed as to adjust the chronometer 
fairly over the centre of the needle, and is then fastened by 
screws. In this state, the magnetic needle below it causes the 
cross and chronometer to traverse with great celerity. It there- 
fore has the property of keeping the chronometer invariably in 
the same position, and, being suspended on gimbals, of preserving 
it from the bad effects of the motion of the ship at sea. The 
magnetic needle was hung five or six inches below the chrono- 
meter, so that its influence on the instrument was not greater 
than that of the earth ; and, being in an opposite direction, has 
a tendency to neutralize, rather than add to, this disturbing 
cause *. 
This apparatus was tried at sea, and proved to answer the 
desired purpose in a most admirable manner. In one of the 
heaviest gales experienced on Captain Scoresby’s last voyage, 
the chronometer on the apparatus traversed perfectly, and was 
steadier than any of the compasses. 
Art. VI.- — Description of Achmite , a New Mineral from Nor * 
way, found and described by P. Strom f. 
This fossil occurs only crystallised. Externally it is of a 
dark brown colour, inclining to red, and in the fracture green- 
ish-black. The lustre of the cleavage is vitreous, and the cross 
fracture dull, but somewhat glistening. It is feebly translucent 
on very thin edges. It scratches glass, and its specific gravity 
is 3.24. It presents a rhomboidal prism, with truncated edges, 
and with very acute summits. It has four cleavages parallel to 
the longitudinal faces of the prism MM re, Plate IV. Fig. 1. 
the two first of which are more perfect than the two last. In other 
directions the fracture is uneven, and nearly earthy. According 
* This instrument is described in the Edin, Trans., vol. ix. p. 364-. 
- -f Abstracted from the Annals of the Academy of Sciences at Stockholm for 
1881, p, 160, 
