June 8, '893J 



NATURE 



127 



but I do not see that the fact has any hostile significance as 

 regards the question a{ identity. 



He will also find that I have always hitherto included the 

 connecting medium as one of the "bodies" between which 

 actions and reactions occur. (See for instance, Phil. Mag., 

 June 1885, pp. 483-84, and October 1879, p. 281). I do not 

 propose to continue to do this in future, partly because I find 

 that the word "body" is not generally or conveniently understood 

 to mean ether as well as ordinary matter, and partly because I 

 now realise that there is something more definite to say con- 

 cerning the function of the ether as regards stre.ss. 



But Mr. Dixon seems to suppose that the denial of action at 

 a distance means that material particles are without influence on 

 one another until they touch ; that for instance the earth cannot 

 attract the moon unless it is in contact with it ; for he says that 

 roy contention that material particles never come into contact 

 renders nugatory the whole discussion i-oncerning "contact 

 action." 



If this be the sort of meaning which he attaches to the phrase 

 "action at a distance," no wonder he is unimpressed with the 

 arguments of those who deny its prevalence in nature. 



Oliver Lodge. 



May I make a few corrections of statements which appear 

 in your report of Prof. Lodge's paper on the Laws of Motion 

 (Nature, p. 117)? 



(i) I do not object to the first law on the ground of unin- 

 telligibleness, but only to the ordinary mode of enunciating it. 



(2) I have not contended that Dr. Lodge's definition of 

 energy as the name given to work done assumes conservation. 

 On the contrary, I have expressly pointed out that it does not. 



(3) I did not select the air-gun with its muzzle plugged as an 

 instance of transference of polential energy without transforma- 

 tion. Prof. Lodge had cited the air-gun as an instance of the 

 transformation of Potential Energy into kinetic during trans- 

 ference. I staled that if the muzzle were plugged it would 

 serve equally well zs an instance of the transference of potential 

 energy without transformation. But I pointed out that both 

 illustrations were defective and proceeded to show that in 

 general the transformation of energy during transference is 

 onlv partial. J. G. MacGregoe. 



Hopeville, Bridge of Allan, N.B., June 5. 



The Word Eudiometer. 



The following quotation from J. A. Scherer's " Geschichte 

 der LuflgUtepriifungslehre " (Vienna, 1785), may be of interest 

 in connection wiih Prof McLeod's letter on the invention of the 

 word " Eudiometer " (Nature, vol. xlvii. p. 536). After referring 

 to Fonlana's Descrizione ed usi di alcnni stromenti per misurare 

 la salubrila dell' aria " (Florence, 1775), Scherer continues {op. 

 cit., vol. i. p. 153), "Bald nach der Herausgabe der gedachten 

 Instrumente machte Hr. Landriani ein neues bekannt, der erste, 

 der es Eudiometer nannte. Er versichert uns er babe seinen 

 Lufteiitemesser von Abt Fontana nicht entlehnt. Daher gehiirt 

 die Ehre der Reformation des Priestley'schen Instruments 

 Hrn. Landriani, die ihm auch Fontana selbst in zwei Briefen 

 einraumt." 



Landriani's own statement quoted by Prof McLeod is thus 

 fully confirmed by contemporary authority. Scherer's book, 

 which has just been purchased for the Owens College from the 

 Kopp library, is full of interesting historical information with 

 regard to eudiometrv. Philip J. Hartog. 



Owens College, May 23. 



Singular Swarms of Flies. 

 Mr. Froude's letter (p. 103) forcibly reminds me of a swarm 

 of flies which overlaid every one who was on the parade at 

 Ventnor, and drove numbers off the pier on the forenoon of a 

 day which certainly fell on or between May 13 and 16, 1891. My 

 diary bears only witness to the fact that I was then at Ventnor, 

 hut I shall never forget that as I went towards the black clouds 

 I met a venerable friend, whose white hair, beard, and light 

 coat were literally blackened with flies. The natives, who had 

 had previous experience of such a cloud, ascribed it to the 

 " mackerel fly." My colleagues in the entomological depart- 

 ment of the British Museum told me I had witnessed a flight of 

 /Hliio Marci (St. Mark's fly), and, on reading up the subject, I 

 found no reason to doubt that they had made an accurate 

 diagnosis of aslighlly and imperfectly told story. 



NO. 1232, VOL. 48] 



I have a definite recollection of the flies' rapid disappearance, 

 and I have very little doubt that Mr. Froude has been the witness 

 of a cloud of the same dipterous insect. F. Jeffrey Bell. 



5, Radnor Place, Gloucester Square, W., June 2. 



P.S. — The weather was very warm during the days menii'.ntd, 

 but the succeeding (Whit) Monday was marked by a fall of snow 

 in several parts of England. Absit omen ! I add this as I noie 

 that Mr. Froude suggestsjthat the special character of the swarms 

 may have some relation to "some condition of the atmosphere." 



The phenomenon so well and exactly described by your 

 correspondent, Mr. R. E. Froude (Nature, vol. xlviii. p. 103) 

 was seen the same day and hour — that is, between I and r.30. 

 May 27— at Parkstone, near Poole, Dorset. A party which had 

 driven over from my house, and lunched at the Harbour Hotel, 

 saw every tree-top crowned, as it were, with asmoke-like column 

 of flies, every column with the same slant one way, desciibed by 

 Mr. Froude, only it was not noticed that this was towards the 

 sun. The strange sight was described to me by my daughter, by 

 word and pencil, last Saturday, immediately on reaching home, 

 and confirmed by her companions. Henry Cecil. 



Bregner, Bournemouth, June 3. 



THE ANNUAL VISITATION OF THE 

 GREEN WICH OBSER VA TOR Y. 



A T the Annual Visitation of this Observatory, which 

 -'*- took place on Saturday, June 3 last, the Astronomer 

 Royal presented his report to the Board of Visitors. 



The present want of accommodation is felt in all the 

 departments of the Observatory, a number of the staff 

 being at present housed in the Octagon room, which 

 forms part of the Astronomer Royal's official residence. 

 The Admiralty have now authorised the completion of 

 the central octagon by the addition of a story and the 

 erection of the Lassell dome over it. 



In place of the old cylindrical dome on the south-east 

 tower, which was dismounted in November last, the new 

 36-foot dome was erected at the beginning of the year, 

 the work of construction and erection being completed 

 most satisfactorily by Messrs. T. Cooke and Sons. 



The electric light installation for the principal instru- 

 ments proposed last year has been sanctioned, and the 

 necessary generating plant, consisting of gas-engine, 

 dynamo, accumulators, and main leads, has been sup- 

 plied. It is proposed to set these up on the ground floor 

 of the new south wing. 



Referring now to the astronomical observations, the 

 work of observing the sun, moon, planets, and funda- 

 mental stars with the transit circle has been considerably 

 increased, owing to the extraordinarily fine weather in 

 the months of March and April, the number of obser- 

 vations being the largest ever recorded. The numerical 

 statement is as follows : — 



Transits, the separate limbs being counted 



as separate observations ... ... ... 8217 



Determinations of collimation error ... 304 



Determinations of level error ... ... 512 



Circle observations ... ... ... ... 7179 



Determinations of nadir point (included in 



the number of circle observations)... ... 461 



Reflexion observations of stars (similarly 

 included) ... ... ... ... ... 527 



The annual catalogue of stars observed in 1892 

 contains 1710 stars. 



The report goes on to say : — 



As an illustration of the continuity of fine weather 

 in March and April, it may be mentioned that 2600 

 transits and 2300 circle observations were made in these 

 two months, the average corresponding numbers for the 

 seven previous years being 945 and 877 respectively ; 

 that 70 observations of upper and lower culminations of 

 Polaris were obtained (exclusive of isolated observations, 

 which are only used for azimuth error and not for place 

 of the star), the average for these months in ten years 



