24, REPORT— 1882. 



persistent labours of Dr. William B. Carpenter deserve the highest com- 

 mendation. 



Our knowledge of tidal action has received a most powerful impulse 

 through the invention of a self-recording gauge and tide-predicter, 

 which will form the subject of one of the discourses to be delivered 

 at our present meeting by its principal originator, Sir William Thom- 

 son ; when I hope he will furnish us with an explanation of some 

 extraordinary irregularities in tidal records, observed some years ago 

 by Sir John Coode at Portland, and due apparently to atmospherio 

 influence. 



The application of iron and steel in naval construction rendered the 

 use of the compass for some time illusory, but in 1839 Sir George Airy 

 showed how the errors of the compass, due to the influence experienced 

 from the iron of the ship, may be perfectly corrected by magnets and soft 

 iron placed in the neighbourhood of the binnacle ; but the great size of the 

 needles in the ordinary compasses rendered the correction of the quadrantal 

 errors practically unattainable. In 1876 Sir William Thomson invented 

 a compass with much smaller needles than those previously used, which 

 allows Sir George Airy's pi-inciples to be applied completely. With this 

 compass correctors can be arranged so that the needle shall point ac- 

 curately in all directions, and these correctors can be adjusted at sea 

 from time to time, so as to eliminate any error which may arise through 

 change in the ship's magnetism or in the magnetism induced by the 

 earth through change of the shijj's position. By giving the compass card 

 a long period of free oscillation great steadiness is obtained when the ship 

 is rolling. 



Sir William Thomson has also eni'iched the art of navigation by the 

 invention of two sounding machines; the one being devised for ascertaining 

 great depths very accurately, in less than one-quarter the time formerly 

 necessary, and the other for taking depths up to 130 fathoms without 

 stopping the ship in its onward course. In both these instruments steel 

 pianoforte wire is used instead of the hempen or silken lines formerly 

 employed ; in the latter machine the record of depth is obtained not 

 by the quantity of wire run over its counter and brake wheel, but through 

 the indications produced upon a simple pressure gauge consisting of an 

 inverted glass tube, whose internal surface is covered beforehand with 

 a preparation of chromate of silver, rendered colourless by the sea- water 

 up to the height to which it penetrates. The value of this instrument for 

 guiding the navigator within what he calls ' soundings ' can hardly be 

 exaggerated ; with the sounding machine and a good chart he can generally 

 make out his position correctly by a succession of three or four casts in 

 a given direction at given intervals, and thus in foggy weather is made 

 independent of astronomical observations and of the sight of lighthouses 

 or the shore. By the proper use of this apparatus, accidents such as 

 happened to the mail steamer Mosel, not a fortnight ago, would not be 

 possible. As regards the value of the deep-sea instrument I can 



