on a New Construction. 293 



P. S. In describ'mg the principles of the polygrammatic 

 telegraph, I avoided entering into the minutiae of its me- 

 chanical construction ; by which, however varied, no funda- 

 mental part of the scheme can be aftected. A model made by 

 my directions in Malta proved to all who saw it the practica- 

 bility of the machine ; I shall, in explanation, say a few words 

 here, which will perhaps be almost equally satisfactory. 



The under part of the posts is solid, but the upper part of 

 them is composed of two side pieces with a space between, 

 within which the arms play. One of the arms is repre- 

 sented in the annexed figure, (fig. 11,) hanging down in 

 its natural position, so as to be entirely hid by the post when 

 the telegraph is at rest. A /oiler A is fixed lo the arm near 

 its head, having an iron ring a, a, a, screwed upon one side 

 of it, and provided with grooves for the strings h, c, the 

 ends of which are fastened to it in contrary directions. The 

 other ends of these strings are brought down into the signal 

 room, and have seven knobs (1,2, 3, 4, 5, 6, 7,) fixed upon 

 them, the intervals between which are proportioned lo the 

 circumference of the roller, in such a manner that as they 

 are respectively pulled down to the plane D, D, they will 

 raise the arm by moving it on its pivot (which coincides 

 with the centre of the roller) to the seven positions required 

 in signal making. As the arm rises to any of these posi- 

 tions, the corresponding tooth of the ring aaa will be 

 griped by one or other of two spriniis or catches fixed to the 

 side piecfS, which will hold it up in its proper position with- 

 out fatigue to the men employed, tdl an order is given lo 

 prepare for a new signal. Then, by pulling another siring, 

 (not expressed in the figure,) the catches are drawn away 

 from the teeth, and the arms being thus released fall clown 

 to iheir natural stale. The same siring, by a very simple 

 contrivance, presses the arms down after the fourth position, 

 and prevents thuir vibratiuL^as they fall at the end of every 

 signal. (/ ri is a piece that would be invisible at the telegraphic 

 distances, serving to increase the weight of the part B as 

 much as may be judged necessary. It was omitted in the 

 model, as not being an essential part of the machine in any 

 other respect. 



T4 It 



