370 Miscellanies. 



ihen will CK, drawn perpendicular to BK be equal to CG. Make 

 BM=EF and draw ML at right angles to BK j then from the prop- 

 erties of similar triangles, BC(=CD) : CK(=CG)::BM(=EF) : 

 LM(=EH). 



To find the points on the ordinates drawn across the circle, through 

 which the periphery of the ellipse will pass, the simple operation is this. 

 Take EF between the points of the compasses and set off that dis- 

 tance from B to M ; then, keeping one point of the compasses on 

 M, close them until the other point sweeps the tangent BK, and set 

 off that distance from E to H ; H will then be a point through which 

 the periphery of the ellipse will pass. Do the like on all the lines 

 drawn for ordinates across the circle ; and through the points, thus 

 found, draw, by the eye, the periphery of the ellipse. This opera- 

 tion is expeditious, and saves the labor of calculating the ordinates of 

 the ellipse arithmetically, and then plotting them ; besides it is less 

 liable to error, excepting when an ellipse is to be projected on a large 

 extent of ground, as for the enclosures of court yards, &c. in such 

 cases an accurate calculation of the lengths of the ordinates is advisa- 

 ble ; but for projections on paper, the rule above given is preferable. 



Albany, April 10, 1833. 



MISCELLANIES. 



FOREIGN AND DOMESTIC. 



Extracted and translated by Prof. J. Griscom. 

 CHEMISTRY. 



1. Preparation of pure nitrate of silver ', by M. Bradenburgh.— - 

 Dissolve in nitric acid the common alloy of silver and copper. Evap- 

 orate to dryness, and heat the salt in an iron spoon till it ceases to 

 boil. Dissolve, then, a very small portion in water, and try it with 

 ammonia to see if any copper remains. If there is, heat it again a 

 few seconds, and make a new trial : as soon as the nitrate of copper 

 is decomposed, pour it on an oiled plate, or dilute the mass in water, 

 and filter it to separate the deutoxide of copper set free by the de- 

 composition of the nitrate. 



2. Decomposition of the chloride of silver in the moist way. — 

 Take a small zinc or cast iron pot ; put the chloride into it, in pieces, 

 and cover it about an inch with water. If the zinc, or iron be per= 



