464 



SCIENCE 



[Vol. LVI, No. 1452 



bodies. Though his publications were com- 

 paratively few — rarely more than one or two 

 a j'ear — he wrote well and painstakingly, and 

 many of his papers will remain among our 

 surgical classics. The one surgeon he perhaps 

 admired more than an5' other was the late 

 Theodore Kocher of Berne, Switzerland, and 

 the two men, in manner and methods surgical, 

 in imagination and ideals, had very much in 

 common. Both of them held their professor- 

 ships for an unusual number of years — Kocher 

 for forty-five years, Halsted for thirty-'three. 



Halsted was a man who taught bj^ example 

 rather than precept. He was a safe, fastidious 

 and finished surgeon, by no means a brilliant 

 and showy operator after the ^tyle cultivated 

 by many of his contemporaries. He eared 

 nothing for administration, and up to ten years 

 ago at least, his staff never met as a body. 

 He was not a successful teacher of under- 

 graduates. A bed-to-bed ward visit was almost 

 an impossibility for him. If he was interested 

 he would spend an interminable time over a 

 single patient, reviewing the history, taking 

 notes, having sketches made, carrying the prolj- 

 lem to the laboratory and perhaps working 

 on it for weeks. Meanwhile his associates and 

 assistants would run his clinic as best they 

 could. In this way his school developed — 

 none of his pupils after his own fashion, to 

 be sure — it would have been impossible to imi- 

 tate him — all of -them, nevertheless, influenced 

 enormously by his attitude toward surgery, 

 and by his operative methods. 



His loss 'to the Johns Hopkins Hospital 

 which he served so faithfully and long, and to 

 which he bequeathed his property, will be ir- 

 reparable. It will be eo.ually so to his many 

 and devoted disciples. One of his long series 

 of resident-surgeons, w^ho, as others have done, 

 came to know him better after leaving his 

 service, just as many sons learn to know their 

 fathers not until after they have grown up, 

 has in all respect and affection written this in- 

 adequate note of appreciation. 



"Who knows whether the best of men be 

 known, whether there be not more remarkable 

 persons forgot than any that stand remembered 

 in the known account of time?" 



H. C. 



EARTH CURRENTS AND MAGNETIC 

 VARIATIONS 



Whenever two metallic conductors are 

 buried in the earth and are connected by a wire 

 through a galvanometer a current is found to 

 flow through the galvanometer. 



Such a current may be (and sometimes is) 

 caused by a difference of electrolytic action 

 upon, or a difference of temperature of the 

 ground plates, but it is often much stronger 

 than could possibly be produced by such 

 action. It is also regularly the case that the 

 farther apart are the ground connections the 

 greater is their potential difference, and this 

 would not be the case if the currents were due 

 to elec-iolysis. Since no one has been able to 

 explain these currents by any of the properties 

 of the metallic part of the circuit, it has come 

 to be believed that the currents are flowing in 

 the earth before the two ends of the wire are 

 grounded, and that the wire merely serves as 

 another conducting path between the two earth 

 connections and acts as a shunt for a part of 

 the current. Thus the currents are not re- 

 garded as flowing around a circuit consisting 

 partly of the metallic conductor and partly of 

 the earth between its terminals, as they would 

 flow if they were electrolytic or thermo-electric 

 currents, but they are believed to flow in the 

 same direction in both the earth and the me- 

 tallic conductor. 



Since no place has been found, either on 

 land or sea, where these currents will not flow 

 through a long conductor whose ends are 

 earthed, it is believed that there are currents 

 flowing everywhere in the outer layers of the 

 earth's crust and in the sea. 



As soon as telegraph lines began to be estab- 

 lished it was observed that currents were often 

 set up in these lines when no battery was con- 

 nected in the circuit. In 1847, a brilliant 

 aurora was observed in Europe and simultane- 

 ously with this telegraph lines were greatly dis- 

 turbed. This led to a careful observation of 

 the diui-nal and seasonal variations of the earth 

 currents which were known to be always 

 present in the lines, and to the establishment 

 of a correspondence between these variations 

 and the diurnal and seasonal variations of the 

 magnetic elements of the earth. Since that 



