296 ‘Scientifie Intelligence. 
_ The transit instrument was made by Ertel and Son, at Munich. Its 
object glass has an aperture of 54 inches, and a focal length of 88 
inches, and was obtained from Merz and Mahler. The axis of the tran- 
sit is 42 inches long. ‘The telescope is formed of two conic frustrums 
of brass, so that the object and eye ends may be readily transposed. 
There are two circles eight inches in diameter for finders, reading by 
two verniers to 10”. The diaphragm contains seven vertical and two 
horizontal permanent wires, anda movable vertical wire. The costof 
the instrument was $1480; the object glass alone $320. ; 
The rural circle was made by Simms, of London, and was received 
in June, 1844. The circle is of brass, and is connected with the central | 
portion by twelve spokes or radii. The whole is one cast., It is divie 
ded into spaces of five minutes each, upon a band of gold inlaid on the 
rim, or perpendicular to the plane of the circle. The telescope has an 
aperture of four inches, and a focal length of five feet. In its focus are 
seven vertical and one horizontal stationary wires, and a micrometer 
wire. Placed at equal distances round the circle are six reading micro- 
scopes. Five revolutions of the micrometer measure five minutes on 
the scale, and the heads are divided into sixty equal parts for seconds. 
Cost of the circle, $3550. 
The transit in the prime vertical, was made by Pistor and Martius, of 
Berlin, and reached Washington in February, 1844. The axis is 42 
inches long. The object glass of the telescope has an aperture of five 
inches, with a focal length of 78 inches. In the focus are placed two 
horizontal and fifteen vertical stationary wires, and one movable ver- 
tical wire. Cost of the instrument, $1750. _ 
The comet seeker was made by Merz and Mahler. It has an object 
glass 3,9; inches in diameter, and focal length of 82 inches. It is 
mounted equatorially, has eye-pieces which magnify from 12 to 50 
times, and cost $280. ; : 
Two astronomical clocks have been ordered, one of Mr. Charles 
Frodsham, London; the other of Mr. William C. Bond, of Boston. 
They cost $300 each. 
The magnetical instrumenis.—The declinometer was made by Mr. 
Barrow, of London. The magnet bar is a rectangular parallelopiped, 
12 inches in length, 0.85 inches in breadth, and 0.27 inches thick. 1 
is suspended in a brass stirrup furnished with a mirror after the manner 
of Gauss. The suspension thread is composed of eight fibres of silk. 
The reading telescope has an aperture of 1-7 inches, and a focal length 
of 21 inches. 
The bifilar magnetometer was also made by Mr. Barrow. It is con- 
structed in the same general manner and of the same dimensions as the 
declinometer. 
