October 10, 1884." 



SCIENCE 



;57 



gine, whether the locomotive is at rest or running. 

 One pole of the dynamo is connected to the locomo- 

 tive, and the other to the tender, which is electrically 

 insulated from the former except through this connec- 

 tion; and the circuit is normally completed through 

 the rails on which the wheels of both are resting or 

 running. In this circuit, within reach of the engi- 

 neer, is a pair of coils whose armature is tightly held 

 as long as the circuit is closed ; but, when it is broken, 

 the armature is drawn away, and opens the valve of a 

 shrill whistle; and it stays away, though the circuit 

 may close again and the whistle continues sounding, 

 until the engineer reaches out and presses the arma- 

 ture up to the coils again, thus compelling his atten- 

 tion and voluntary action to stop the whistle. At 

 any point or series of points in the line, where it is 

 desired to signal to or from the approaching train, 

 pairs of rails are inserted, electrically insulated from 

 each other; so that, during the instant while the loco- 

 motive-wheels are on one pair and the tender-wheels 

 on the other, the circuit will be broken and the alarm- 

 whistle set going, unless these rails are otherwise con- 

 nected. 



They are thus connected by wires leading from the 

 pairs of such rails ahead to any desired points, — to 

 signal-stations, to switches, to drawbridges, to cul- 

 verts, or bridges, or any part of the track or road- 

 bed liable to be washed away or rendered dangerous. ' 

 Thus, so long as the signal-man does not open this 

 circuit, so long as the switch or drawbridge is not 

 open, and the culvert, bridge, and road-bed are safe, 

 the circuit keeps closed through these loops, the engi- 

 neer gets no signal, and he runs on with confidence. 

 But if any thing is wrong ahead, or if the man in the 

 signal-tower wishes to signal the oncoming engineer, 

 these loops will be open, the circuit will be broken, 

 and the whistle set going till the engineer voluntarily 

 stops it. Moreover, the instantaneous current sent 

 from the dynamo over these loops when closed can 

 signal the approach of a train, from as far as desired, 

 to the signal-man at a crossing, to the train-despatch- 

 er, to the switch or bridge tender: in fact, to any points 

 from one end of the line to the other the continuous 

 flashes of this dynamo-current can be made a perfect 

 tell-tale of the progress of the train. Moreover, these 

 same currents can be made to lock switches and draw- 

 bridges ahead of the approaching train from pairs of 

 rails preceding the danger-signal ones; and the engi- 

 neer can thus confidently approach such places at 

 full speed, knowing that no careless or confused 

 switchman or bridge-tender or evil-disposed train- 

 wrecker can have thrown these open after he has 

 passed the locking signal-rails, and then, from an- 

 other pair of rails beyond, the dynamo unlocks them 

 after the train has passed. A signal on the throttle- 

 valve lever warns the engineer if he attempts to run 

 out of the round-house without starting up the dyna- 

 mo, and any subsequent failure in the dynamo also, 

 of course, blows the warning-whistle till it is set right. 

 This system, in which each locomotive is its own un- 

 failing battery, has certainly important advantages, 

 especially in compelling the attention and voluntary 

 action of the engineer whenever danger is ahead. 



THE COMMITTEE REPORTS OF THE 

 AMERICAN ASSOCIATION. 



Although several committees were discharged 

 last year for making no report, there were no less 

 than eleven to be called on at the session on Monday 

 morning. Of these, six made no response whatever: 

 others, only a verbal and partial statement. The 

 following reports are of general interest: — 



Dr. E. B. Elliott of Washington, the chairman of 

 the committee on the registration of births, deaths, 

 and marriages, said that this committee was created 

 many years ago to petition the United States con- 

 gress for the establishment of a system of registra- 

 tion of births, deaths, and marriages. Since many 

 states have established systems of registration of 

 their own, the committee has petitioned, not for a 

 separate system, but for the co-operation of the gen- 

 eral government in securing uniformity and efficiency 

 in the several state systems. 



The first report of the committee on stellar magni- 

 tudes (Proc. Amer. assoc, xxx. p. 1) included a 

 plan for the cleterminatiozi of standards for stars 

 fainter than the tenth magnitude. Twenty-four 

 bright equatorial stars were chosen; and the stand- 

 ards were to be selected from the regions following 

 them from two to six minutes of time, and not dif- 

 fering in declination from the leading stars by more 

 than five minutes of arc. The second report pre- 

 sented this year consists of charts of all the stars 

 visible with the fifteen-inch telescope used at the 

 Harvard college observatory, in all but three of the 

 regions from which the standards are to be selected. 

 These observations have been verified by the fifteen- 

 inch telescope of the Washburn observatory. The 

 report was referred to the publication committee. 



The committee to confer with committees of for- 

 eign associations for the advancement of science, 

 w 7 ith reference to an international convention of sci- 

 entific associations, reported that they had succeeded 

 in conferring with a like committee from the British 

 association. 



A motion to have the committee discharged, as it 

 had completed its task, having been made, Prof. H. 

 Carvill Lewis of Philadelphia asked whether the 

 committee might not continue to be efficient in ex- 

 tending courtesies from our own association to kin- 

 dred foreign associations. Many gentlemen felt that 

 some steps should be taken whereby members of our 

 association going to England may become members 

 of the British association while there, and a like 

 courtesy be extended to members of the British asso- 

 ciation while in America. He therefore suggested 

 that the action on the motion to discharge the com- 

 mittee be deferred for the present, in the expectation 

 that arrangements would be made for the holding of 

 joint meetings by the two great associations. 



Mr. Trelawney Saunders of London, Eng., said he 

 should like to respond in a few words to the kindly 

 sentiments that had been expressed from the plat- 

 form. As an Englishman, he said that he was 

 delighted to hear the sentiment — a general senti- 



