August 23, 1883] 



NATURE 



405 



THE EDISON-HOPKINSON DYNaMO- 

 ELECTRIC MACHINE 



THE following abstract of the report by Mr. Frank S. Sprague 

 on the Edison-Hopkinson dynamo-electric machine will be 

 found of interest to electrical engineers : — ■ 



Characteristic features of the dynamo are : General arrange- 

 ments — those of a shortened and differently proportioned Edison 

 dynamo. The pulley, however, is outside of bearing, and with 

 a face of 6f inches and diameter of 10 ! , T inches projects 8^ inches 

 outside the base plate. Field coils wound over a 9-inch core with 

 ten layers of No. 16 copper wire (B.W.G.). Two legs in series. 

 Armature: Diameter of core 9 inches, 74 c uls, single turn, 8 

 strands of No. 16 wire, average length 43 inches. Wire bound. 

 Diameter loi inches, with T V inch clearance from pole faces. 

 Zinc plate connecting pole faces ; ends of magnets not scraped. 

 Resistances: Field cold, 365 ohms ; armature cold, '026 ohm!!. 

 Field measured ; armature calculated. Field warm, 37 ohms ; 

 armature warm, '0325 ohms. Power supplied from a Lawrence 

 — Armington and Sims — engine, high-speed and non-condensing, 

 driven by a link belt through an Alteneck tension belt dynamo- 

 meter. 



Engine diameter 84 inches accepted. 



Stroke 9{» inches measured. 



Piston-rod 1 5 inch ,, 



Fly-wheel 40 inches ,, 



Indicator spring 56 inches „ 



2 . P. L. A. revs. 



I-H.P. = ; 



P. 9K 

 12 



2 . _ 



33,000 



(2'425--j,; = ). revs. 



Sj'ooo 

 = Mean pressure X rev. X 002S107. 

 The magnets were tested by the Poggendorff method. 



Total H magnetic field = Gr X E X posltlon 



resis. X dif. 

 E = 1-457 Clarke's standard 

 Gr = 642S 

 Mean force in laboratory — Westminster : — 



Earth. No. 45. No. 17. 



May 7 - I2i ... 9*41 ... 1140 



May 8 -122 ... 9-46 ... n*4S 



May 12 T22 ... 9"40 ... 1152 



Total H field for Manchester :— 



E and No. 45 9-55 



E and No. 17 11 '61 



The results of three fairly full loads are given. No. 6 Time, 

 about one hour ; load, 192 lamps and ground of about 5 

 amperes. Lamps not up to candle power. 



Potential galvanometer, magnet .. 

 ,, ,, position . 



,, ,, strength . 



Average deflection 



Potential at brushes 



Current galvanometer, magnets 

 ,, ,, position 



,, ,, strength 



Average deflection 



Current in lamp circuit 



field 



,, armature 



Resistance, lamp circuit 



and field 



Total resistance of circuit 



E.M.F . 



Electrical energy in lamp circuit 

 „ „ field ... . 



,, ,, armature 



Total 



Dynamometer spring at rest ... . 



,, ,, running free . 



,, ,, load 



Total difference 



Above friction 



Total power to armature 

 Power above friction 



Friction 



No. 4S 

 2 



9-55 



2079 



99-27 



No. 17 



2 



n-6i 



1939 



112-56 



2-68 



"5' 2 4 



•882 ohms. 

 ■861 



•8935 

 102-97 



H'97 

 ■30 

 ■58 



volts. 



amp. 



volts. 

 H.P. 



7' 



Dynamo speed, 10S1 ; engine speed, 289-3 ! efficiency of con- 

 version, 97-7 per cent. ; commercial efficiency, 86-3 per cent. 



Dvnamo behaved well. Fields cold. Armature moderately 

 warm. Wrist not uncomfortable on coils. Can also be held on 

 commutator. Little sparking. 1 Bearings cool. No increased 

 heating after standing. 



The same remarks about the behaviour of the dynamo are 

 pertinent to two later experiments with 192 and 230 lamps re- 

 spectively. There was no appreciable increase in the heating, 

 and the load could easily have been carried a long while. An 

 increased load of 30 lamps could be carried some time. 



Summary of Three Experiments 



Means : 04 '8 7, 86 '/„ 



INDIAN METEOROLOGY 

 I. 

 ■pXPERIENCE only confirms what a cursory glance would 

 '—' have led us to anticipate from theoretical and a priori con- 

 siderations — that meteorology, the most modern as well as nne 

 of the most ancient of all the sciences, requires to be studied on 

 the largest possible scale. The synoptic chaits of the late 

 General Meyer in America, of Hoffmeyer in Germany, and our 

 own Meteorological Office, have graphically and forcibly set 

 before us the variety and complexity of conditions that occur in 

 a horizontal direction, while the observations of balloonists and 

 mountain travellers have equally illustrated the important differ- 

 ence and often complete opposition which exists between the 

 physics of the upper and lower aerial strata. Indeed it may be 

 affirmed of meteorology, with even more truth than of the 



analogous science of geology, that it recognises neither political 

 nor superficially physical divisions of the land. When, there- 

 fore, we confine our attention to the atmospheric conditions of 

 one small political division of the earth's surface and attempt to 

 educe from data collected within that region alone the laws 

 which regulate them, we are in a far worse position — especially 

 if we take the British Islands as our example — than if we essayed 

 to construct the science of geology by a like process, since in the 

 latter case, if our horizontal range is limited, these islands fcrm 

 an almost complete and unique epitome of geological strati- 

 graphy. In the ca=e of meteorology, however, it is far other- 

 wise, since our area is not only microscopic in relation to the 

 scale on which meteorological changes occur, but is situated in a 

 peculiarly unfavourable position for studying those changes with 

 success. 



1 Some lateral play of armature and spindle. 



