6 
THE TELEGRAPH. 
planks of various shapes painted black, and which could be 
raised between slides. 
Telegraphy by means of opaque bodies has continued in use 
for ships, especially as a means of indicating to mariners the 
heights and movements of the tides in ports. For this purpose 
balls with black bands are hoisted up on an apparatus formed 
of a mast and a yard. These balls stand out quite black against 
the sky. A ball placed at the intersection of the mast and 
yard indicates a depth of water of three metres throughout 
the whole length of the channel. Each ball placed on the 
mast below the first, adds one metre to the depth of water; if 
placed above it adds two. A ball hoisted at the end of the 
yard represent a quarter of a metre when it is to the left of 
the mast, and half a metre when it is to the right. Therefore 
only six balls are required to indicate the depth of the water, 
each quarter of a metre from three metres to eight and three- 
quarters. 
These signals may be made at night by substituting lanterns 
for the balls, and using a coloured light to mark the point at 
which the yard crosses the mast. 
To indicate the flow of the tides, a white flag with a black 
cross, and a black pendant in the form of a vane are used. 
These flags are hoisted as soon as there are two metres of 
water in the channel, and they are taken away when the water 
has again come down to that level. During the flow of the 
tide the pendant is above the flag; at the time of high water 
the pendant is taken away; and during the ebb the pendant 
is below the flag. 
When the state of the sea prevents entrance to the port, all 
these signals are replaced by a red flag, also hoisted on the top 
of the mast. 
This digression has withdrawn ns a little from the history of 
visual telegraphs, but we thought the foregoing details would 
not be without interest. 
Bertin, in his “ Curiosites de la Litterature,” informs us 
that the Marquis of Worcester laid claim to the invention of a 
hundred new machines, and asked Charles II. of England a 
certain sum of money to make them known. This v T as 
refused. It has been said that the telegraph and the steam- 
