242 



NATURE 



[January 12, 1893 



ally, we are told, the systems consist of a separate hot- 

 water circulating system in each car, in connection with 

 a heater, fed by steam from the locomotive, by a con- 

 tinuous train pipe running the length of the train, and 

 coupled together between the cars by flexible hose-pipes 

 and universal couplings ; the Sewall steam coupler being 

 generally used. Another important railway necessity is 

 the continuous brake. Under this heading the latest form 

 of Westinghouse quick-action automatic brake is de- 

 scribed. In the original design the brake is applied by 

 the engine-driver allowing a little air to escape from the 

 train pipe, lowering the pressure, and thus applying the 

 brake by the automatic action of the triple valves. It is 

 evident that the vehicle next the engine will feel this 

 reduction first, and its triple valve will work before that 

 on the second vehicle, and so on. On trains of ordinary 

 length this very slight difference in time between the 

 brake's application on each vehicle is of little consequence, 

 but when this automatic brake is fitted to a long goods 

 train it becomes a serious matter. The length of a goods 

 train of fifty American cars is 1900 feet, and the brake 

 should act instantaneously to be perfect. The new triple 

 valve is itself designed to discharge air from the train 

 pipe ; so on the driver opening the driver's valve, allow- 

 ing air to escape to apply the brakes, the reduction of 

 pressure operates the triple valve on the first car ; this lets 

 out more air, and so on through the train, the brake on 

 the last car, F900 feet away, being operated in 25 seconds 

 after that on the first car. 



The vacuum automatic brake is not described or illus- 

 trated. This brake is now being more and more brought 

 into use. and for general purposes it appears to be simpler 

 and less liable to get out of order than its competitors. 



A considerable part of the volume is taken up with the 

 applications of electricity, for lighting and motive power 

 purposes generally. On dynamo electric machmery much 

 has been written and well illustrated. The reader is 

 taken step by step from the rudiments of the subject to 

 its latest applications, from a description of armatures to 

 the arrangements of the field-magnets, then to the vary- 

 ing designs of dynamos, including most of the known 

 machines. The same may be said on the treatment of 

 the electric motors. Under the head of the transmission 

 of power there is more useful information to be found, 

 this being all the more interestmg, because of the pro- 

 posed use of electricity as a means of transmitting some 

 of the power of Niagara to distant towns. There is, how- 

 ever, something wanting under the heading of electrical 

 measurmg instruments. The only ones mentioned are 

 Weston's volt and ammeters. At the present time the 

 street tramways of this country are in an uncertain stage 

 as far as motive power is concerned ; horse-power is 

 admittedly expensive ; the steam locomotive seems to 

 have got into disrepute ; the cable and electric traction 

 appear to be struggling for the mastery. It is interesting 

 therefore to read the memoir on electric traction in this 

 volume. The accumulator system is just described, but 

 the overhead cable or trolley system takes up the greater 

 part of the space, so it is safe to assume that the latter is 

 more gmerally in use, the principle of which is as fol- 

 lows : the current starts from the positive brush of the 

 dynamo, passing out to the main conductor, suspended 

 over the middle of the track, and along this conductor 

 NO 12 11, VOL. 47] 



until it reaches the point where the trolley of one of the 

 motor cars is in contact. Here it divides, and a portion 

 passes down through the trolley to the motors, and 

 thence to the rails forming a return lead to the negative 

 brush of the generator. The main portion of the 

 current passes on to feed other cars upon the line in the 

 same manner, each car taking the quantity of current 

 necessary to develop the required power. There are at 

 the present time nearly 500 electric railways in America, 

 and taking the results of twenty-two electric trolley lines, 

 we find that the expenses vary per car mile from 22*99 

 cents to 789 cents, the highest and lowest respectively. 

 A view is given of the electric street railway at Washing- 

 ton, D.C. ; the overhead conductors being not at all 

 unsightly. 



On electric welding there is also much information, 

 the Thomson process being very fully described. It 

 consists briefly in completing the electrical circuit 

 through the parts to be welded together, the resistance 

 being sufficient to heat the parts so as to weld them, this 

 being assisted by pressure. 



The Bernado process is not described ; in this process 

 the work to be welded is connected to one terminal of 

 the dynamo. The positive terminal being connected 

 with a carbon rod, held in a portable insulated holder, 

 the carbon rod is then placed on the work, and im- 

 mediately withdrawn slightly, thus forming an arc, 

 where the metal melts, and with skill much can be 

 done. 



The locomotive practice in America has long been of 

 interest to locomotive engineers in this country, owing to 

 the many differences in design and practice. A very 

 good resume of American practice is to be found in the 

 memoir under this heading. A useful table is given 

 showing a few leading dimensions, weights, &c., of typical 

 engines in use. Take, for instance, the express passen- 

 ger engine, a four-coupled bogie engine, the cylinders 

 being 20 inches in diameter and 24 inches stroke. The 

 driving or coupled wheels are 72 to 78 inches in diameter. 

 The weight un coupled wheels is 75,000 pounds (33'48 

 tons), the total weight of the engine being 1 16,000 pounds 

 (5178 tons), and that of the tender 72,000 pounds (32-14 

 tons. Comparing these data, we find that the American 

 engine is heavier than an 18x26 cylinder British engine 

 and not so powerful, assuming equal steam pressures % 

 the tender is light in a similar comparison, probably 

 carrying less water. The reputed weight of trains hauled 

 given in the table is of little use, because the speeds are 

 not given, and for this reason comparisons cannot be 

 made. 



The paragraph on locomotive boiler construction is 

 far too short ; many interesting details might have been 

 added. It is stated that the circular smoke-box tube 

 plate is a coni-picuousr dif^eieice btiween the practices 

 of the two countries, being purely American, whereas 

 the Midland Railway Company have, amongst others, 

 used the arrangement lor some time. Owing to the 

 enforced use 01 anthracite cc al in teitain parts, many 

 peculiar designs of loct moiive boiJeis have been used, 

 the Wootien boiler being proLably the most common. 

 All, however, have particularly large grate areas, which, 

 in the case of the Wooiten, may in some cases exceed 

 76 square feet, or four times the area of the grate of. 



