676 REPOET — 1882. 



A still larger boat is under construction for the Russian Government ; she will 

 be 113 ft. long by 12 ft. 6 in. beam, with a displacement of 58^ tons. Her contract 

 speed is the same as that of the Danish boat, but will be obtained under severer 

 conditions, "to secure that the trial trip speed shall be maintained on actual service. 



Relatively to the Whitehead torpedo, the Spar torpedo must be considered as 

 a torpedo with a spar 10 yards, as compared with one having a spar 400 yards 

 long, that being the range at which the Whitehead torpedo may be considered 

 tolerably effective. Yet the Spar torpedo is not to be looked on as obsolete, and in 

 the hands of a seafaring population, trained to the use of torpedo-boats, it would 

 prove most efiicient. In circumstances such as prevailed at the bombardment^ of 

 Alexandria, when the attacking ships were so enveloped in smoke that the firing 

 had to be suspended, it is a question whether the Spar torpedo would not have 

 been both the most certain and the least hazardous weapon of attack. The 

 English first-class boats are now being armed with the Spar torpedo as an 

 alternative armament. 



In conclusion, the author pointed out the importance of a properly-organised 

 torpedo service for coast defence botli at home and in our colonies, and particularly 

 for our scattered coaling stations, which, in the exigencies of a great war, might 

 be left a prey to any adventurous captain. A disaster to our navy, or the_ calls 

 that might be made upon it in a great war, might leave our harbours and navigable 

 rivers temporarily exposed to the attack of an enemy, and although no one would 

 propose that torpedo boats should take the place of forts and land defences, yet the 

 knowledge of their presence, and the risk of being struck at any moment in his 

 most vulnerable part, would compel an enemy to approach our forts with far 

 greater circumspection than was considered necessary in encountering the heavy 

 guns of the Alexandrian batteries. 



3. Current Meter Observations in Hie Tidal Compartment of the Thames. 

 By Professor W. C. UxwiN, M.I.C.E. 



These observations were made witli the object of testing a new form of current 

 meter made by Messrs. Anisler Latl<Mi. of Schatfhausen, and also to examine how 

 far current meter observations could ' e usefully carried out in a tidal river. 



The current meter is a screw cunv nt meter, differing from those ordinarily used 

 in the mode of suspension, and in h:-. lug an electrical signalling arrangement. The 

 meter is carried in gimbals and is fiee to move in any direction. A long conical 

 rudder keeps the screw normal to the direction of the stream. Tlie meter is sus- 

 pended in the water by a steel wire ^\ith a weight of 40 kilogrammes below it. A 

 small crab or winch for lowering out or raising the meter carries an index, show- 

 ing the exact depth of the meter from the water surface. The author found the 

 arrangement to work extremely well, the conical rudder appeared to have adequate 

 directing power and the meter held i' s proper position in the water with very great 

 steadiness. At every 100 rotations of the screw, an electrical circuit is made which 

 rings a bell above water. To obtain t1ie rate of rotation, it is therefore only neces- 

 sary to note the time of 100 or 200 or .500 revolutions by a chronograph stop-watch. 

 The velocity of the water is obtained fmm the number of rotations observed, by a 

 suitable formula, with constants deirnuined by previous experiments. 



In ordinary river gauging, the difficulty of obtaining accurate restdts arises, 

 chiefly, from the variations of velocit at each point due to the unsteady motion of 

 the water and the eddies superpose! 'H the general forward motion. In a tidal 

 stream, there is the additional diffioul . that the velocity is periodically varying with 

 the continuous change of the depth ..^ 1 surface slope. 'That observations in a tidal 

 stream should be of any use therefore, it is very necessary that they should be made 

 with considerable rapidity. In the e:, ■ . ■ iraents here described the author took entire 

 charge of the current meter, alterin^ •:- position, noting the time, and recording the 

 revolutions himself Nevertheless '.n the average of six days' work, one velocity 

 was obtained on the average every tin oe minutes, a degree of rapidity very satis- 

 factory. 



The observations were all taken - ^ nj? vertical, in water varying with the phase 



