Feb. 20, 1890] 



NATURE 



369 



occurs in Nevis, whence the Zoological Society received living 

 specimens (presented by Mr. Graham Briggs) in 1870. 



The only West Indian island in which Quadrumana of the 

 American type occurs is Trinidad, which was, doubtless, 

 formerly part of the mainland of South America. 



3 Hanover Square, W., February 17. P. L, Sclater. 



Galls. 



I HAD not intended to take any further part in this corre- 

 spondence ; but the interesting suggestion which has now been 

 made upon the subject by Mr. T. D. A. Cockerell (Nature, Feb. 

 13, p. 344) induces me to withdraw the sentences that he quotes 

 from my previous letters, to the effect that it seems impossible 

 to imagine any way in which galls can be attributed to natural 

 selection acting on the plants directly. In my own consideration 

 of the matter this seemed " obvious," and therefore my motive 

 in taking up the difficulty as presented by Mr. Mivart was that 

 of " asking whether anybody else had a better explanation to 

 offer" than the one which my letter suggested — viz. "that 

 natural selection may operate on the plants indirectly through 

 the insects," by always selecting those insects the character of 

 whose secretions is such as will best cause the plants to grow 

 the particular kind of morphological abnormality which the 

 larvae require. Mr. Cockerell, however, has now furnished what 

 seems to me an extremely plausible hypothesis, showing that 

 there is a way in which it is quite conceivable that the growth 

 of galls may be an actual benefit to the plants, and therefore 

 that natural selection may act directly on the plants themselves 

 in evolving these sometimes highly specialized structures for the 

 use of their parasites. Mr. Cockerell informs me in a private 

 communication that he has been verifying this hypothesis by ob- 

 servations in detail ; but whether or not he will be able to 

 establish it, I think at any rate he has done good service in thus 

 suggesting another possibility. 



On the other hand, I cannot see that Mr. Ainslie Hollis has 

 helped us at all (Nature, January 23, p. 272). For he merely 

 enunciates the truism that trees which were not endowed with 

 sufficient "developmental vigour" adequately to resist the 

 attacks of gall-making insects " would doubtless have long ago 

 succumbed in a struggle for existence." And this truism he 

 appears to suppose furnishes an explanation of how " natural 

 selection, operating in the ordinary manner," has produced galls 

 for the exclusive benefit of the insects. But it is obvious that 

 the more detrimental the growth of galls has proved to trees, 

 the less reason there must have been for natural selection, 

 "operating in the ordinary manner," to have developed these 

 often highly specialized structures for the benefit of parasites. 



London, February 13. George J. Romanes. 



The Supposed Earthquakes at Chelmsford on 

 January 7. 



Nature for January 16 (p. 256) reprints from the Essex 

 County Chronicle a short account of two supposed earthquake- 

 shocks felt at and near Chelmsford on January 7, at 12.30 and 

 1.25 p.m. Being engaged in the study of British earthquakes, I 

 made inquiries in the district referred to, and the result of these 

 is to show that the shocks were almost certainly due to the firing 

 of unusually heavy guns at Woolwich. It may be worth while 

 to state the evidence for this conclusion somewhat fully, as it 

 will be difficult to obtain it in after years. 



(i) I applied to the authorities at Woolwich and Shoeburyness 

 as to the nature of the firing on January 7. At the latter place, 

 the only practice was from 9-inch and lO-inch guns, the maximum 

 charge used was 70 pounds of powder, and therefore not 

 capable of producing the shocks felt at Chelmsford. At Wool- 

 wich, however, the no-ton gun, *^ the heaviest in H. M. service,''' 

 was fired at the times mentioned. 



(2) Form of the Disturbed Area, — The only accounts I have as 

 yet received are from the following places : Great Warley 

 (near Romford), Brentwood, Epping, Ingatestone, on the road 

 between Ongar and Fyfield, Roxwell, Chelmsford, Chignall 

 St. James, and Chipping Hill (Witham) ; which are respectively 

 at about 6, \2\, 14, 16, 16, 21, 24, 24, and 32 miles distance 

 from Woolwich. Referring to a map of Essex, it will be seen 

 that these places all lie close to a line drawn from Woolwich in 

 a north-easterly direction ; with the exception of Epping, the 

 direction of which is about north by east from Woolwich. Ac- 

 cording to the Times weather report of January 8, southerly and 



south-westerly breezes prevailed very generally throughout the 

 kingdom on the previous day. 



(3) Nature of the Shock.— In four cases, the shock was in the 

 first instance attributed to the firing of heavy guns. If there was 

 any vibration of the earth, it must have been very slight, and the 

 following descriptions seem to leave little doubt that the rattling 

 of windows noticed was due to an air-wave. 



Great Warley — The shock " broke a pane of glass 4 feet x 2 feet 

 on my job." 



Brentwood — "The shocks commenced as a low rumble, in- 

 creasing till the doors shook and rattled, as though the rumbling 

 was followed by a bang or explosion." 



Between Ongar and Fyfield (the observer driving) — "The 

 ground felt as if it were sinking," and there was "a rumbling 

 noise something like guns in the distance. " 



Roxwell — The sound "exactly resembled the report of the 

 big guns at Shoebury, but was far louder than we usually hear 

 them." 



Chelmsford (the observer walking) — There was "a noise as of 

 a very heavy weight being rolled across the floor of the room of 

 the house to the south of him, which he was passing." 



Chignall St. James — " The shock was extremely slight, but 

 there was a most pronounced concussion in the air which made a 

 sound on the windows as if a person had thumped the centre of 

 the window frame with the soft part of his hand. There was no 

 tremulous motion felt." 



Witham— The observer "heard a strange rumbling sound 

 which seemed to slightly deafen him, but he felt no vibration of 

 the earth." 



That the disturbances recorded had only one origin is, I think, 

 evident, (i) from the decrease in intensity (roughly speaking) as 

 the distance from Woolwich increases, and (2) from there being 

 no considerable gap between the places of observation. Records 

 from the immediate neighbourhood of Woolwich could hardly be 

 expected, as there they would naturally be attributed to their 

 proper source. 



I am indebted to the editor of the Essex County Chronicle for 

 inserting a letter asking for observations on the shocks, and to 

 several gentlemen for the courtesy and kindness with which they 

 replied to this letter and to other inquiries that I made in the 

 surrounding district. Charles Davison. 



38 Charlotte Road, Birmingham, February 13. 



Shining Night-Clouds. 



In July last, on a fine night, about 8 p.m. (two hours after 

 sunset), I noticed a fleecy cloud lit up by a yellowish light, 

 directly over the back of a range of hills due west from this 

 place. As it did not move, it struck my attention, and I 

 observed that what little wind there was carried the few floating 

 clouds north-east to south-west. I continued to watch the 

 cloud, which covered say 4° or 5°, until li p.m., and concluded 

 that as in that direction lay the Purace volcano, about 40 miles 

 away, the light and cloud probably came from it. But I made 

 inquiries by telegraph, and found that no eruption had taken 

 place in the Purace, which has been quiet now for many years. 

 I regret, seeing now that the subject is interesting, that I did 

 not observe more carefully. I may add that in the direction of 

 the cloud no prairie or forest fire could have occurred to account 

 for it. Robert B. White. 



Agrado (lat. 2° 20' N.), Department of Tolima, 



U.S. of Colombia, S.A., December 22, 1889. 



A Greenish Meteor. 



To-night (Jan. 30), at 8.15 p.m., I saw a meteor which, not- 

 withstanding a bright moon, shone out exceedingly brightly, 

 exceeding any star. It appeared to travel south, for about 10°, 

 vanishing about 15° above the horizon. Its colour differed from 

 that of any meteor I have seen before, being pale green or 

 greenish. T. D. A. Cockerell. 



West CUff, Custer Co., Colorado, January 30. 



THE MOLECULAR STABILITY OF METALS, 

 PARTICULARLY OF IRON AND STEEL. 



(1) A LLOW me to add some words relative to the very 



-^~^ timely lecture on the hardening and tempering- 



of steel, recently published by Prof. Roberts-Austen 



