Qgo Mr. Seppings o?i a new principle of constructing 
and securing ihem with iron pins in the form of a square ; 
which on the least pressure may be made to change its form 
to the rhombus ; but let another piece be fixed to it diagon- 
ally, and the figure of the frame will be found immoveable. 
Place a bar in the middle parallel to two of the sides, and 
secure it firmly by iron pins, still the figure will easily be 
moved by the hand, like a parallel ruler, and assume the 
rhomboidal shape of A or B; but apply to the frame what the 
carpenters term the brace in a common field gate as Z, and 
the figure will remain, as before, immoveable. 
'Zr 
0 
0 
0 
0 
0 
' 
If this brace or diagonal piece is not fixed to it, the outer 
part of the gate (or that part most distant from the hinges) 
will have a constant tendency downwards, until at length it 
will reach the ground. 
Let fig. 1 and 3 represent two frames of wood composed 
of parts strongly connected by bolts or iron pirn?. 
Fig. 1. Will represent the principle on which the present 
system of ship building is conducted. 
