Nov. 13, 1884] 



NA TUBE 



29 



Fourteen days ago, when on the Fraser River, eighty miles from 

 here, I saw after sunset a very brilliant aurora borealis. I write 

 this thinking there may be a repetition of the phenomena in 

 England, in which case this note may possess interest. 



G. W. LAMPLUGH 

 Victoria, Vancouver Island, October 13 



Peculiar Ice Forms 



The ice structures observed by Mr. Woodd Smith (November 

 6, p. 5) are evidently the same as were described in vol. xxi. 

 p. 396. I have often seen such fibrous masses since, under cir- 

 cumstances which left no doubt rf their being mainly due to 

 prolonged condensation of aqueous vapour from the air ; the 

 fibres, white like asbestos, and covered only by a very thin layer 

 of earthy particles, rising from a hard subsoil. The absorption 

 of aqueous vapour by the soil, especially on mountains, seems 

 not yet to be duly appreciated, although it is prove! by the 

 many springs issuing at short distances below the summits, and 

 has been insisted upon already in Er. Darwin's " Botan. Garden " 

 and " Phytonomia " (chap. xi. 2). "Rainfall being the source 

 of all water-supply" (Nature, vol. xxx. p. 375) is a statement 

 hardly to be maintained. W. 



Freiburg, Badenia, November 8 



Seismographs — An Apology 



I am just in receipt of the inclosed letter from Mr. Charles A. 

 Stevenson, in which he claims the original idea of the actuating 

 mechanism in the horizon'al component seismograph I have lately 

 described in these pages, and he includes a copy of his paper to 

 jnstify his remarks. I therefore think it my duty to offer my 

 apologies to him for not having given him full credit for his 

 invention so far as it goes, although I have unconsciously done 

 him wrong. Naples is unfortunately very badly off for modern 

 sciemific works and Proceedings of Societies, both as regards the 

 National and the University libraries, and as far as I know no 

 copy of Mr. Stevenson's paper exists in the town, except the one 

 he has now sent me. 



Perhaps I may be permitted to point out that Mr. Stevenson's 

 seismograph, so far as it is described, would be almost useless 

 for the following reasons : — 



(1) The inertia of the upper glass plate would be insufficient 

 not to be affected by the slight movement conducted through the 

 ivory balls to it. This is the reason I use the very heavy lead 

 disk. 



(2) No earthquake shock is perfectly horizontal, so that Mr. 

 Stevenson's instrument would only be fit to register the hori- 

 zontal component of the earth-wave, and would fail to do this, 

 since if the angle of emergence was appreciable it would be 

 jerked up off its supports, and consequently would simply register 

 a series of interrupted lines. This is why I introduced the upper 

 balls and resistance plate. 



(3) If the instrument was disturbed by an earth-wave of large 

 amplitude, the registering arm would pass beyond the border of 

 the smoked plate (unless the apparatus was of very great dimen- 

 sions, so failing to fulfil the conditions of the British Association), 

 where the needle would drop out, or fall so low as to prevent 

 the return of the arm over the plate. 



(4) If the earthquake was of some seconds' duration and com- 

 posed of many varying movements, as is generally if not always 

 the case, a network of irregular curves would remain on the 

 glass that would be quite unintelligible. 



If a thing is to be done, it is advisable to do it well, and it is 

 less possible to have accurate registers of earthquake shocks than 

 of the force and direction of the wind, barometric pressure, or 

 any other meteorological phenomena. The requirements of the 

 British Association with regard to expense, size, and portability 

 of seismographs, will not permit anything like an accurate inves- 

 tigation of geodynamics. 



In conclusion, should I have overlooked and appropriated the 

 ideas of any other inventor, I shall be happy to fully acknow- 

 ledge them if sufficient evidence is given (as in the above case) 

 of priority of publication. II. J. Juhnston-Lavis 



November 7 



45, Melville Street, Edinburgh, November 3 



I noticed recently in Nature (vol. xxx. p. 608) an article 

 by you in which you describe a seismograph for recording earth- 

 quake shocks, which would appear to be your own invention 



from reading the paper. No doubt the method of making the 

 record, springs, and upper balls are your own invention, but the 

 principle on which the seismograph there described acts is, as far 

 as I know, mine or my father's. I inclose the paper in which it 

 was first described, and I would be glad to learn from you if you 

 forestalled me. Charles A. Stevenson 



Dr. Johnston-Lavis, Naples 



Fly-Maggots Feeding on Caterpillars 



A FEW months ago I had a caterpillar of Papilio erythronius, 

 which I found on a lemon-tree. I put it into a card-box, and 

 fed it daily on lemon-leaves. The box was covered with cloth 

 tied tightly all round the opening. After some days, the cater- 

 pillar fixed itself to the side of the box, and turned into a 

 chrysalis in the usual way. One day on opening the box, 

 instead of finding the chrysalis changing into its usual colours 

 and markings, it was dark all over. A few days more, on re- 

 opening the box, I found six fully-developed cream-coloured 

 maggots at the bottom of the box. I was rather puzzled to con- 

 jecture how these maggots got into a box three inches high, with 

 a bit of cloth tied all round the opening. I put the maggots into 

 a little box with some earth under a tumbler. They immediately 

 buried themselves in the earth. In a few days I found six 

 chrysalides, and some days later there were six ordinary house- 

 flies buzzing within the tumbler. I then examined the dark 

 chrysalis of the P. crythronius, which was evidently dead, and 

 found it only a shell. All its interior had been consumed by the 

 six maggots. It is evident that these maggots in their infant 

 stage had already been in the body of the caterpillar when I 

 boxed it. The latter had gone through its transformation as if 

 nothing was the matter with it, although, if one could have 

 interrogated it, probably it would have complained of mysterious 

 gnawings and creepings in its interior. A time, of course, came 

 when, for want of nerve-centres and other organs, the chrysalis 

 could not go on with its development into the perfect Papilio. 

 The six maggots having had a full meal, found their way out of 

 the Papilio's chrysalis in order to undergo their transformation. 



I knew that the larvae of the Ichneumonidas fed on the live 

 bodies of caterpillars, but I did not know that the larvae of the 

 house-fly did so also. E. Bonavia 



Etawah, India, October 18 



THE CRYSTALLINE ROCKS OF THE 

 SCOTTISH HIGHLANDS 

 "PVER since the discovery of Silurian fossils in the 

 *-* rocks of North-West Sutherland, it has been recog- 

 nised that in that region lies the key to the structure of 

 the Scottish Highlands. Accordingly, when in the pro- 

 gress of the Geological Survey, the mapping of the High- 

 lands had to be undertaken, I determined that a detailed 

 survey of the Sutherland ground on the scale of six inches 

 to a mile should be made as a basis for the work. In the 

 summer of last year a surveying party under the charge 

 of Mr. B. N. Peach was stationed there, with instructions 

 to begin by mapping the Durness Basin. This duty was 

 satisfactorily accomplished before the end of the season. 

 The Silurian series of Durness was ascertained to be 

 about 2000 feet thick, and to consist of numerous successive 

 zones, which were traced on the six-inch maps and dis- 

 criminated in such a way as to be recognisable should 

 they be found to occur in the more complicated region to 

 the east. With this necessary groundwork well esta- 

 blished, the Eriboll tract was attacked this summer by 

 Messrs. Peach and Home. I had never myself had an 

 opportunity of studying the Eriboll sections, which, from 

 the days of Macculloch down to the present time, have 

 been such a fruitful subject of discussion. It was a 

 special injunction to the officers now intrusted with 

 the detailed survey of the region to divest themselves 

 of any prepossessions in favour of published views and to 

 map the actual facts in entire disregard of theory. By 

 the close of this last season the structure of the Eriboll 

 area had likewise been traced upon the six-inch maps, 

 and I then went north to inspect the woj'c. From time 



