40 
MINUTES OF PROCEEDINGS OF 
The manner of operating is then shortly as follows:— 
A fort points out an object, and makes known its position by telegraph. 
The principal station details the two forts that are to observe and also the 
one that is to direct and indicate the moment of observation in the case of the 
object being moveable. The observers announce when they have found the 
object, point at it, and read the angles to the telegraph operators who transmit 
them to the other stations, when by means of the threads and divided circles 
they are laid down upon the charts. 
A point of intersection is thus obtained, which represents the position of 
the ship or object at the moment of observation, and after having marked this 
point in pencil, its distance from the fort or battery is measured by a divided 
scale, graduated so that distances of 25 feet can be read off with facility. 
At the fort “ Provesteen ” the distance thus found is communicated to the 
casemate battery by means of an acoustic tube. 
In the regulations, of which a copy is appended, are collected all the details 
relative to the measure of distances both of fixed and moveable objects which 
accord with those given by me in the original scheme. 
These regulations are based upon the results of daily experiments carried 
on throughout the summer of 1864, which succeeded so well that the distances 
of moveable objects were determined with great precision with only half 
minute intervals between the observations. Such observations are now 
directed to be made at intervals of one minute, in order that the observers 
may work with greater certainty. 
The trials above alluded to were principally made upon the numerous 
steam boats passing in sight of the fortfications, whose tracks were marked 
out upon the charts. 
In general each ship was not observed more than five times, but its course 
was sometimes followed for a longer time, and the operations were only sus¬ 
pended for a short time, when for the purpose of obtaining greater nicety in 
the points of intersection, one of the observing forts was replaced by another. 
Errors made in the measurement of angles (an advantage of the graphical 
method) are easily recognized by the abrupt change in direction of the ship's 
track. 
The simultaneous observations of three forts afford a means of testing the 
proper adjustment of the zero points of the theodolites. Plotting the angles 
and measuring the distances upon the chart present no difficulties whatever. 
The graphical method has also the advantage of clearly depicting the 
movements of a ship, and thereby exposing the reasons by which its course 
is governed, facts which would be of great importance when the system of 
defence comprises the use of submarine mines or torpedoes. 
In most cases it is possible to determine with sufficient accuracy the 
position which a ship will occupy at a given future moment, and thereby to 
regulate the explosion of torpedoes laid down in its track, so as to obtain the 
greatest possible effects. 
Another interesting application of this method is the determination during 
practice of the points of impact of shot fired from the various batteries. 
We will give one example which happened when firing at long ranges. 
The target was placed at 8200 feet from “ Provesteen," and at 10,400 feet 
from the “Trekf oner/’ where after having observed and plotted upon the 
