184 τ  REPORT—1850. 
Px & Ps (fig. 1. Plate 1.), are stone pillars whose common centres are in 
the mean magnetic meridian (about). 
Q Q are two of four brass tubular columns. 
qg' and @? are screws and nuts which enter and clamp those four columns to 
two marble slabs. 
R is the lower slab of black marble resting on P¥. 
r? 72 are bolts and nuts which firmly secure the magnet support upon R. 
S is the support of and apparatus for raising and lowering the magnet of 
Dr. Lloyd’s construction, but without the cross wires, &c. 
s!, the base. 
85, four leveling screws. 
85, pieces carrying the agate pallets. 
85, frame-work moveable by means of a key, &c., for raising the magnet 
off from its pallets. 
T, a squared brass tube passing through V into A. 
X is the upper black marble slab carrying A, G, a', K', &c.* 
Some minor improvements have been made in the apparatus used for the 
preparation, &c. of the Daguerreotype plates, viz. on the polishing board, 
Plate I. fig. 3; the buffs, fig. 4; the coating boxes, fig. 5; and the burning- 
off and fixing stand, fig. 6. 
The Polishing Board. 
A (fig. 3. Plate I.) is the mahogany board. 
a‘ a‘ are screws which attached it to a firm table. 
B is a piece of mahogany attached to A by means of two screws. 
δ᾽ δι are the two screws which pass through it and screw into A. 
δ δὲ are two pins fixed firmly in B but sliding stiffly in A. 
63 is a rim (or edging) of thin sheet brass attached to A’and projecting 
upwards a little less than the thickness of a photo-plate. 
δ᾽ is ἃ similar edging of sheet brass attached to B. 
The surfaces of 6° and b* are always in exactly the same plane, and the 
photo-plate may be firmly held between them by using the screws 6! δ). 
The Buffs. 
A (fig. 4.) is a deal board | inch thick in the middle and ξ inch at each 
end. Its lower surface is bellied (in the manner of a large file), and covered 
first with flannel and then with thick plush cotton velvet. It is rubbed across 
the plate. Its handle (a') is glued and screwed firmly upon it. 
The Coating Boxes. 
A (fig. 5.) is the deal box. 
αἱ αἱ are the usual openings in its sides. 
a? is the door which carries the usual mirror (on its interior face). 
αὐ a are strips of mahogany with screws and washers which fix them upon 
the edges of A but allow them to be approached towards, or withdrawn 
from each other a little, in order that any sliding-frame, as H, may fit exactly 
between them. 
a* is a little projecting piece to support the glass plate below mentioned. 
B is the glass cistern fitted into A, and containing crystals of iodine, distri- 
buted on the bottom. 
δ᾽ is the glass plate cover of B resting on its upper edges and projecting 
beyond A. 
H is the sliding-frame containing the photographic plate (or paper) and 
* This vertical-force magnetograph was shipped for Toronto on the 23rd of March, and 
Captain Lefroy, the Director of the Royal Observatory of Toronto, has acknowledged the 
arrival of it as well as of the horizontal-force magnetograph, I understand that he has 
mounted and successfully worked this latter instrument. 
