Physics and Chemistry. 377 
examined, the dome must be revolved about ninety degrees 
from the first position above described. In this way, by turn- 
ing the dome in four positions, all parts of any vertical circle 
can be examined. 
It is evident that with an instrument eccentrically placed the 
dome has to be slightly larger than in the ordinary case. To 
accomplish this, some additional expense must be incurred, but 
it is believed that this expense will be a small item if it allows 
the construction of a better form of shutter. 
the conditions of easy motion are in this form fulfilled. 
The weight of the shutter rests on a railway, and not a pound 
has to be lifted. The friction on the railway and on the pintle 
ean be reduced to a very small quantity. There should be no 
SCIENTIFIC INTELLIGENCE. 
J. Puysics AND CHEMISTRY. 
1. On the Chemical Activity of Zinc on which Copper has been 
deposited —Several months ago, GuapsTonE and T ripe announced 
that zine on which copper had been deposited, was capable of de- 
amyl and methyl iodides. The couple was prepa by pouring 
4 solution of cupric sulphate, containing about 1°5 per cent of the 
salt, upon a crumpled piece of zine foil, about the thickness of 
ned in an ounce 
Velvet, 
NOG Atanas t 
mk lodide is poured upon this couple, 
Place at ordinary temperatures ; but, at t 
a ’ ib lved, and there 4 geo 
Ho alline bod kland’s zinc ethiodide. e 
i chocea ich har PRPS ser until all the ethyl 
hed h an 
lodide disa ay ‘> body was then heated in a 
ram ppeared. ‘The crystalline Y hich distilled over was 
