TRANSACTIONS OF SECTION G. 781 



Tvitliin the cable to tlie top, whence it descends by the latter to the earth. Unless 

 the continuity of the testing wire and cable be good no current ^N-ill pass, and the 

 needle remains still. On depressing B a cnrrent is sent in the opposite direction 

 through a resistance-coil to the earth. If the needle be deflected, the apparatus is 

 proved to be ready for the resistance test, which is made by the depression of keys 

 A and B both at the same time. The current then divides itself equally between 

 the circuit formed by the insulated wire and conductor, and a resistance which 

 should be made exactly equal to the other circuit ; this being so, any defect in the 

 lightning conductor would manifest itself by the needle not balancing, but showing 

 a deflection. In such a case key C is brought into use, and its depression at th& 

 same time as B shows whether the earth of the conductor is good, or if the fault is 

 to be looked for above ground, as the current is then divided between B and 0, 

 whose resistances are equal. 



A very sensitive galvanometer needle is required, as a good conductor of average 

 length would only be about T^^tli of an ohm. One having the needle suspended by 

 a silk fibre above, and kept in position by another such fibre below, will respond 

 not only to j^th of an ohm, but even to joW*^ thereof. 



5. On an Organisation for the Systematic Gauging of the Wells, Springs, 

 and Rivers of Great Britain. By Joseph Lucas, F.G.S. 



It has long been felt by engineers and others that tbere should be a survey of 

 the sources of water-supply in this country. In the last few years several isolated 

 observers, anticipating any general organisation on this behalf, have been registering 

 various items of account, such as the variation in the level of water in wells, but 

 they have never been collected and brought side by side with others, sucb as the 

 rainfall, percolation, barometric pressure, and temperature, all of which influence 

 the supply, or collated and reduced to perspective on maps, except over a very 

 limited area in the South of England. 



This very isolation, however, greatly impedes the usefulness of the work, and 

 it is very desirable that an influential committee should be appointed to direct and 

 systematise these separate efibrts, and to take charge of the work till it is finally 

 committed to responsible hands. 



There is a committee of this Association, founded in 1874, and there is another- 

 of the Meteorological Society, at work upon underground water. Mr. Baldwin 

 Latham has a large series of wells, springs, and rivers under observation, and there 

 are several other observers at work in various parts of the country. 



This, however, is a task too large for individuals or even societies, and should,, 

 the author thinks, be executed at the public cost. Since April last, he has been 

 receiving returns of gaugings and other observations on surface and subterranean 

 water-economy from observers in various parts of England, and these returns, two 

 of which are now ready, will be published monthly till some better arrangement 

 can be made. Until this time amves the author will gladly receive observations 

 from any observers of the variations in the wells, springs, and rivers of these islands,, 

 and supply proper forms, and the returns as they are published, to anyone who may 

 take an interest in any of the various aspects of the water question. 



6. On a Dynamometer Coiipling. By Professors W. E. Ayrton, F.B.S.y 

 and John Peret, B.E. — See Section A, p. 553. 



7. On the Lawyer's Marine Pocket Case. By Capt. Bedford Pim, B.N^ 



