124 ANNUAL OF SCIENTIFIC DISCO VEEY. 



mentioned likely to change or disturb it. When the head of an iron 

 vessel was at right angles with the slip on which she was built, then 

 the compasses would be affected by the permanent magnetism ; when 

 her head was turned toward her building slip at an angle of 45, then 

 her compasses were affected by the inductive magnetism. A vessel 

 in heeling over port or starboard would be most likely affected when 

 standing north and south, and a ship proceeding from one hemisphere 

 to the other would be most affected when standing east and west. 

 The lecturer then entered into a series of elaborate illustrations, 

 showing the calculations which should be made in dealing: with a 



CJ ^^ 



subject which was surrounded by so much difficulty. Thus far their 

 investigations had but showed them how little reliance could be placed 

 on the compass at all. It required constant watching, and they might 

 always suspect that it was affected by the magnetism of the iron of 

 which the vessel was constructed. One result of the introduction of 

 iron in shipbuilding operations must be the employment of masters 

 and mates of superior education. 



BONELLI'S ELECTKIC TELEGRAPH. 



For many years the attention of telegraphists and the hopes of the 

 public have been directed to the possibility of automatically repro- 

 ducing an original dispatch ; but difficulties, apparently insuperable, 

 have militated against all realizations of the project. The electric 

 telegraph, recently devised by Signor Bonelli, the inventor of the 

 electric loom (see Annual of Scientific Discovery, 1861, p. 113), is, 

 however, an immense stride towards the attainment of this end, even 

 if it be not perfection itself. We will endeavor to describe the prin- 

 ciple of the new system, as exhibited in the Great International 

 Exhibition of 1862. 



Let the reader suppose himself to be the operator ; before him he 

 will find an oak table, six or seven feet in length, seventeen to eigh- 

 teen inches wide ; along the centre of this table runs a miniature rail- 

 way, terminated at either end by a spring buffer, and spanned mid- 

 way by a kind of bridge six inches in height and two and a half or 

 three inches wide. Upon this railway is placed a species of wagon, 

 one yard long and five inches wide, three and a half in height, run- 

 ning upon four brass wheels ; on the surface of this wagon are two 

 long rectilinear openings the one occupying the upper half and 

 destined to carry the message which is to be sent, the other occupy- 

 ing the lower half, and intended for the message which may be to be 

 received ; upon the bridge are two small metal combs, each contain- 

 ing a number of insulated teeth, answering in number to, and con- 

 nected with, the insulated conductors of which the line is formed. 

 The combs differ from one another ; the one which is to dispatch the 

 message, being formed of so many teeth having a certain freedom of 

 action, is on the side of the bridge farthest from the operator ; the 

 other, or writing comb, is formed of a similar number of teeth fixed 

 in a block of ivory, and forms a perfect line, which rests with a slight 

 but regular pressure transversely on the paper, and occupies the 

 nearer portion of the said bridge. We will suppose that the tables 

 have been tested, and that a number of messages have been sent for 



