Feb. 6, 1879] 



NATURE 



315 



Force and Energy 



Your correspondent, Mr. R. H. Smith (Nature, vol, xix. 

 p. 194), speaks of "the fine old crusty Newtonian maxim . . . 

 •force is any CAUSE which,' &c." Now Newton's words are 

 these : " DeBnitio IV. — Vis impresja est actio in corpus 

 EXERCITA, ad mutandum ejus statum vel quiescendi vel movendi 

 uniformiter in directum." It will be observed that Newton 

 avoids the use of the obnoxious word cause. I suppose that 

 ome translator, or commentator on Newton, adopted the word 

 • • cause " (in the sense, probably, not of an efficient cause in 

 itself, but, by a common figure of speech, of the action of some 

 cause), and that other writers transcribed the expression. 



Prof. Tait, who is specially referred to by your correspondent, 

 seems to have overlooked the above definition when he WTote 

 (" Recent Advances," ed. i.p. 16) : "the definition of force in 

 physical science is implicitly contained in Newton's ' First Law 

 of Motion,' and may thus be given : Force is any cause,'' &c. 

 Newton, in that law, speaks of "vires impressae," but forbears 

 there to define, or explain, "vis." Clearly he refers back to 

 Def. IV., where, as I have shown, he defines "vis impressa"' 

 by "actio," not by "causa." 



In justice to Prof, Tait, however, it should be pointed out that 

 in the passage referred to he proceeds at once to discuss the diffi- 

 culty introduced by the word "cause." He has, in fact, antici- 

 pated your correspondent in the idea of his definition of force. 

 Prof. Tait vs-rites thus : "In every case in which force is said to 

 act, what is really observed ... is either a transference or a 

 tendency to transference of what is called energy from one por- 

 tion of matter to another. Whenever such a transference takes 

 place there is relative motion of the portions of matter con- 

 cerned, and the so-called force in any direction is merely the rate 

 of transference of energy per imit of length for displacement in 

 that direction." J. G. H. 



Electrical Phenomena 



Mr. Green, in his letter to Nature, vol. xix. p. 220, omits 

 to state the route by which he ascended Monte Rosa "not long 

 since." This is a detail of interest, because the rocks of that 

 range are decidedly magnetic, and much hidden on the north 

 side by ice. 



In 1875, much out of sorts, I was training by short clirnbs, 

 and at the Kiffleberg, well known for its effect upon the 

 magnet, strolling up the Gomer Grat in company with three 

 other members of the Alpine Club, and several more, the sky 

 quickly clouded over, it thundered, and the axes of the Alpine 

 men fizzed in most orthodox fashion, especially when held up, 

 and the long sticks of the non-climbing men also crackled. A 

 transitory but vivid lightning storm followed. 



Several days later, during an attempt to ascend the Stockhom, 

 in company with a young Englishman, from the north side, 

 by the Triftje glacier, the same fizzing, concurrently with 

 snow, thtmder, and lightning, took place, and half up the last 

 glacier a violent storm came upon us, and throwing caution to 

 the winds, we both skeltered down the snow and ice slopes with 

 scant respect for crevasses seen and hidden. But for the 

 mountaineer's axiom, "never part with your axe," Me were 

 much inclined to throw ours on one side. Soon we got below 

 this critically charged stratum of air and earth, and the fizzing 

 ceased. I shall never forget that terrible half hour, only to be 

 imagined by moimtaineers or seafarers, Forbes, in his splendid 

 work on glaciers, relates a similar incident somewhere in this 

 same range. 



Positive and negative changes of earth and air, conductibility 

 of these and of axes, and involuntary experimenters su^t^est 

 themselves. In our latter case all were more than damp ! 



I have not Forbes' bock here, and can therefore quote no 

 details. Thunderstorms are characteristic. In 1849 (I think it 

 was) I made a new pass, called the Neue Weiss Thor. Over- 

 head it was fine. A mile below was a thunderstorm, and during 

 our descent on the Italian side, we came into it, and were 

 refreshed first by snow, then by rain, till we reached Macuguaga. 



Marshall Hall 



Vemex-Mcntreux, Canton Vaud, Switzerland, January 27 



Ear Affection 

 S^TERAL years ago, during an attack of whooping-cough, I 

 found that one of my ears was so affected as to cause sounds 

 heard by that ear to seem flatter than their true pitch as heard 



by the other ear. The difference was about a semitone, as I 

 ascertained by holding a timing-fork to each ear alternately ; and 

 when I whistled I heard two notes in discord. The affection 

 lasted about ten days. 



Will one of your readers kindly render me an explanation. 



Adelaide, November, 1878 P. 



RELATION OF METEORITES TO COMETS' 



T HOLD in my hand a stone that weighs about two and 

 ■■• a half pounds. Over a part of its surface is a thin 

 black crust. A part of its comers are cracked off, showing 

 a gray interior, and on looking closer you see small 

 points of iron all through it. It is heavy — about one half 

 heavier than granite, or marble, or sandstone. Alto- 

 gether it is a very curious stone, totally unlike any of our 

 rocks. 



That stone ivas once a part of a comet. 



Do you want my reasons for saying it ? Or, does any 

 one doubt it ? I propose to-night to give those reasons ; 

 to set in order, as clearly and simply as I can, the facts 

 and lines of thought that lead me to say as I did — that 

 stone was once a part of a comet. 



It came to us from Iowa. Three years ago, on Feb- 

 ruary 12, about ten o'clock in the evening, the light of a 

 bright meteor was seen by nearly everybody then in the 

 open air in the south-east part of that state, I will quote 

 from a vivid description of the meteor given by Mr. 

 Irish, a civil engineer of Iowa City, who has collected 

 and published many facts about it : "The observers," he 

 says, "who stood near to the line of the meteor's flight, 

 were quite overcome with fear, as it seemed to come 

 down upon them with a rapid increase of size and 

 brilliancy, many of them wishing for a place of safety, 

 but not having the time to seek one. In this fright the 

 animals took a part, horses shying, rearing, and plunging 

 to get away, and dogs retreating and barking with signs 

 of fear. The meteor gave out several marked flashes in 

 its course, one more noticeable than the rest. . . . Thin 

 clouds of smoke and vapour followed in the track of the 

 meteor. . . . From one and a half to two minutes after 

 the dazzling, terrifying, and swiftly moving mass of light 

 had extinguished itself in five sharp flashes, five quickly 

 recurring reports were heard. The volume of sound was 

 so great that the reverberations seemed to shake the 

 earth to its foundations ; buildings quaked and rattled, 

 and the furniture that they contained jarred about as it 

 shaken by an earthquake ; in fact, many believed that an 

 earthquake was in progress. Quickly succeeding, and 

 blended with the explosions, came hollow bellowings and 

 rattling sounds, mingled wnth clang, and clash, and roar, 

 that rolled away southward, as if a tornado of fearful 

 power was retreating upon the meteor's path." 



From accounts collected from eye-witnesses by Prof. 

 Leonard and Mr. Irish, I conclude that the meteor when 

 first seen was not less than sixty miles high over Northern 

 Missouri ; that it descended at an angle of about 25° with 

 the horizon, in a right line, and disappeared at a height 

 of five or ten miles. Those in the east, as at Kiokuk, 

 saw it low in the west. From St, Louis it was seen in the 

 north-west. In the western part of Iowa it was seen to 

 pass north across the eastern sky. To persons in the 

 north it passed straight down on the southern sky, while 

 to those imder the path named it passed nearly over- 

 head, rising in the south and south-west and descending 

 in the north north-east. The path thus determined is at 

 least 120 miles long, and was passed over in a few 

 seconds, probably not over ten. The country near the 

 explosion was prairie or alluvial, where stones on the 

 surface are rarities, and about 800 lbs. of stones like this 

 one, nearly 200 in number, have been picked up in a 

 region seven miles by foiu", a little east of the end of the 



' A lecture delivered in the Mechanics' Course at tie SheSeld Scienti^c 

 School cf Yale College, U.S., by Prof. H. A. Xewion. 



