Sept. 14. 1882] 



IV A TURE 



495 



feature in this proposal is that of driving the chalk cutting 

 machinery by hydraulic power, the waste water being discharged 

 into a vessel with the chalk debris. Chalk "cream," is then 

 formed by the revolution of a drum in this vessel, and this cream 

 is pumped to the head of the working and di-cbarged. 



Three papers were read by Major Allen Cunningham R.E., 

 whose recently published work in connection wi h the Hydraulic 

 Experiments at Roorkee, gives this country a position with 

 regard to the subject, which it certainly could not previously 

 claim. The following are brief extracts : — On unsteady Motion in 

 Open Channels: The motion of water in open channels is 

 essentially an unsteady motion with intirlacing stream lines ; 

 the hypothesis of steady parallel motion is at variance with 

 nature. Single velocity measurements are of little practical use, 

 being only accidental value-; ; the average of a large number is 

 pretty constant, so that the average velocity should always be 

 sought. The time needed to obtain ihese involves a chance of 

 change of the external conditions. In practical hydraulics the 

 forward velocity is the only velocity considered or required. 

 Floats measure this directly; no other instruments yield this 

 quantity readily in large streams. The-e principles are of great 

 importance, and show that hydraulic experiments must always 

 be tedious and expensive. — Convexity of the Swfacc of Streams : 

 The figure of the transverse section of the free surface of a 

 stream, usually supposed to be convex, is here considered. 

 The evidence is shown to be very small. Some new special 

 experiments are cited. The conclu-ion is that the surface is 

 probably level across. — Depression of Maximum Velocity: The 

 line of maximum velocity in an open channel is usually below 

 the surface. The cause of the depression is ob-cure. The 

 wind and distubances from the banks and bed are usually 

 supposed to be the causes. The wind is probably too incon- 

 stant. The disturbances from the banks and bed seem an 

 inadequate explanation. The general depression of the maxi- 

 mum velocity on all verticals at all parts of a channel indicates 

 some resistance from above. The motion in open channels and 

 in rivers flowing full shows some similarity with differences in 

 detail fairly accounted for by supposing the air to be an ever 

 present efficient drag or source of resistance to forward surface- 

 flow, less intense than the banks or bed. If this be admitted the 

 hydraulic term "wet border " must be modified so as to include 

 all parts of the wet border, each with its own specific resistance. 



On Compressed Air as applied to Locomotion, by Sir F. J. 

 Bramwell. — The author dwelt upon the cases in which com- 

 pressed air might be advantageously employed for this purpose, 

 as for instance in the proposed Channel Tunnel and on tramways. 

 For the latter, some altered means of traction seems for several 

 reasons inevitable. One of these reasons is the undoubted 

 cruelty to horses which is the result of the present system. The 

 fact that compressed air can be satisfactorily used for this pur- 

 pose is proved by the tramways of Nantes, which for ihree years 

 and a quarter have been worked by this means. The various 

 difficulties to be expected on any tram-line, such as those from 

 curves and gradients, are to be found on that one which, running 

 beside the River Loire, connects Doulon and Chantonay. The 

 cars run every ten minutes from both ends of the line for fifteen 

 hours each day in summer, and fourteen hours in winter, and 

 during the time above mentioned there has been no hitch what- 

 ever. An arrangement called the " Hot Pot " is used to obviate 

 the loss of energy and the inconvenience arising from the well- 

 known fact that air becomes heated when being compressed, 

 and cools upon expansion. The apparatus consists of a vessel 

 of water into which steam is forced at the conclusion of each 

 journey. Through this heated water the compressed air is 

 passed, and is thus at the same time heated and lubricated. An 

 ingenious form of regulating-valve was also described, by means 

 of which a uniform working pressure is maintained, whatever 

 may be the pressure in the air reservoirs. The two contrivances 

 are combined, and together effect : (1) a great saving of power, 

 and (2) a trustworthy mode of regulating the pressure. Details 

 of the engines and pumps at the stations were given, these to- 

 gether working with the high efficiency of 82 per cent., that is, 

 with a loss of only 18 per cent, of the total energy. The ex- 

 penditure of fuel per day, under the conditions already given, 

 is only t\ tons of coal, or a little more than \2\ lbs. per mile 

 run. 



Three papers were read by Dr. Fleming. The first upon 

 Recent Progress in Electric Railways was practically a descrip- 

 tion of an experimental railway laid down by Mr. Edison in 

 Menlo Park. The plan there adopted is to connect one rail at 

 regular distances with one of the terminals of a dynamo in a 



central station, the other rail being similarly connected with the 

 opposite terminal. The motor has externally the appearance of 

 an ordinary locomotive without a funnel, containing, however, a 

 dynamo, by means of which short circuiting between the rails is 

 prevented, and the motive power obtained. The percentage 

 of useful effect claimed by the authot was exceedingly high, 

 only 5 lbs. of coal per hour per H.P. being used, as against 

 6 lbs. with an ordinary locomotive. A speed of 40 miles an 

 hour, over 8 or 10 miles, was stated to have been attained. 

 These statements of the author concerning the efficiency of the 

 system described by him, were called in question by the Pre- 

 sident, Prof. Forbes, and others, who complained of the meagre 

 supply of facts upon which to form an opinion on such an im- 

 portant question. Dr. Werner Siemens, at the request of the 

 President, made some remarks with reference to his own ex- 

 perience in electric railways, stating the loss of power to be one- 

 fifth in winter, and one-eighth in summer. Amongst other 

 things he advocated overhead connection of wires to convey the 

 current. The other papers by Dr. Fleming were upon electric 

 lighting and the efficiency of the Edison dynamo. 



Prof. Forbes described a very simple and ingenious form of 

 electric lamp, and then read a paper giving results of experi- 

 ments on wires conveying currents, which he had embodied in 

 two laws. These laws define the strength of current which can 

 be sent through wires of different diameters without raising the 

 external temperature above a certain limit. Law I. When the 

 wire is bare and exposed to the air, the strength of current is 

 proportional to the diameter of the wire. Law II. When the 

 wire is wound in coils of the same size and weight, the strength 

 of current is proportional to the diameter of the wire. To dis- 

 cover the first law, a thin coating of wax was put upon each 

 wire, and a current gradually increasing in strength was passed 

 through it until the wax melted. The strength of the current 

 was then read off on a galvanometer. To discover the second 

 law, two equal tubes were wound with many layers of wire until 

 they were of equal weight ; these were filled with water and a 

 thermometer bulb inserted. The currents required to raise the 

 temperature in each equally were measured. 



Mr. Barlow read a paper On the Mechanical Properties of 

 Aluminium. This metal is used chiefly as a substitute for silver, 

 but the author had found it to be exceedingly strong in propor- 

 tion to its weight. Experiments had been caret ully mode for 

 him by Prof. Kennedy, from which its valuable properties of 

 ductility, tensile strength, and elasticity were fully demonstrated. 

 This was well illustrated by the comparative le gth of rods 1 f 

 uniform section, but of different metals, which could be sus- 

 pended without rupture, the lengths in the case of steel and 

 aluminium being equal and exceeding all others. Unfortunately 

 it is an expensive metal, and the process by which it is at present 

 extracted leaves little hope of its use being greatly extended. 

 Sir H. Bessemer said he did not think any metal could be de- 

 pended on like the one in question, from the small part its weight 

 took in producing its rupture. He exhibited a key of the mate- 

 rial (about the size of a large latch key), and it was stated that 

 45 °f these would only weigh one pound. 



Mr. A. Giles read a paper on The Southampton Docks. This 

 paper was listened to with considerable interest, from the fact of 

 proposed local changes, which, if carried out, w.uld consider- 

 ably affect the port. The paper not only gave a history of the 

 present works, and dealt with the future improvements, 1 ut 

 also gave statistics of the trade of the docks as a commercial 

 undertaking. 



Mr. Price Edwards read a paper On Sound Signals, discussing 

 the various signals used on railways, ships, and the coast. He 

 stated that a change was about to be introduced in connection 

 with the Trinity House signals, in which a combination of high 

 and low notes was to be used. A trial of explosive signals was 

 also shortly to be undertaken. Allusion was made to the 

 unnecessary shrillness of railway whistles. 



Prof. W. C. Unwin read a paper on Current Me'er Observa- 

 tions in the Thames. The author described and exhibited the 

 instrument which he had used. This meter differs from most 

 other meters in its mode of suspension, being 1 wered into the 

 water by a stout wire from a boat, proper orientatian being 

 secured by a tail or vane. The instrument is very convenient to 

 use, observations being taken by one observer at an average rate 

 of one in three minutes. The results obtained were exhibited 

 by curves. 



Sir F. J. Bramwell exhibited and explained the action of a 

 speed indicator. This instrument had be>-n designed a d em- 

 ployed by him in connection with experiments upon railway 



