THE ROYAL ARTILLERY INSTITUTION. 
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constantly kept. The table, on which the instruments stand, is of very 
solid construction, and rests upon a large solid flagstone embedded in 
concrete, and perfectly insulated from the flooring. At each side of this 
table smaller tables are constructed, the greatest care being taken that they 
do not touch the large table. The room is furnished with presses, tables, 
shelves, and all the necessaries of an instrument room. A barometer and 
thermometers of the very best construction, serve to denote the atmospheric 
changes. 
19. The voltaic batteries are arranged on small shelves in an outer 
room, and the connecting wires between the voltaic batteries and the several 
parts of the instrument, as well as from the instrument and batteries to the 
main wires, are copper wires of 0‘05 in. diameter, insulated with gutta 
percha. The main wires consist of ordinary galvanized iron wire of 0T6 in. 
diameter, stretched on posts to the targets. 
20. The gun battery is at a distance of 225 ft. from the instrument 
room. The battery consists of two platforms laid parallel to one another at 
a distance of 10 ft. apart. Tn front of these platforms screens are placed, at 
a distance of 20 ft. These screens are of the most solid construction, and 
faced with sheet iron; a slot, and movable slider, serves to regulate the 
size and height of the hole through which the projectile has to pass. At 
2 ft. in front of each platform pickets are driven into the ground, and all 
measurements with regard to the distance of the targets are made from these 
pickets; in practising, the muzzle of the gun is brought over the picket. 
21. From each picket a horizontal distance of 150 ft. is accurately 
measured, following a line perpendicular to the hurter of the platform; at 
the extremity of this distance a flagstone is firmly set in concrete, and a line 
drawn on the stone marking the distance; from this flagstone a horizontal 
distance of 120 ft. is set off towards the platform, and another flagstone set; 
the targets rest on these flagstones. The first target is therefore at a 
distance of 30 ft. from the picket, and the second target at 120 ft. from the 
first, and at 150 ft. from the picket; the point midway between the targets is 
therefore 90 ft. from the picket. Both ranges are parallel, and exactly the 
same, and, as has been stated, at a distance of 10 ft. from each other. 
22. Other flagstones are placed at intermediate distances, so that the 
targets can be moved to within 60 ft. of each other when operating with 
small charges, and consequently low velocities. 
23. A line of posts, bearing the wires, comes from the instrument room 
to the first target, and the wires are then continued by a post to the second 
target. 
24. The targets consist of two parts, the frame, and the target. 
The frame is formed of wood, in the manner before described (Sect. 9); 
and the targets can be hung up on the frame, by means of hooks 
and eyes. The targets are made of very hard wood and are 30 by 40-in., 
a row of hard wooden pins, 1*5 in. apart, are driven into the sides of the 
