74 



NA TURE 



{Jan. 19, 1888 



It would be interesting to hear of funher observations of this 

 bright meteor. It must have been seen by many persons, as the 

 night was very clear. 



The fireball of February 21, 1S65, had a radiant at 255° + 55", 

 and close to that of the meteor of January 2 last, but the differ- 

 ence of date is too considerable to permit an inference that the 

 wo bodies diverged from the same stream. 



January 8. W. F. Denning. 



In Nature, November 10, p. 36, it is stated in. reference to a 

 meteor that " a Norwegian astronomer" is of the opinion that 

 the track of the meteor must have lain too high to be heard. 

 " He calculates from the reports to hand that the bursting of the 

 meteor occurred at an altitude of about 6000 feet [sic), and he 

 thinks that even this figure may be safely doubled." 



It may interest some of your readers to know that on the night 

 of July 3, 1884, at 8.27 p.m. standard time of the 75th meridian, 

 a meteor was seen by me, as well as by others, here, and about 

 fm, 17s. afterwards a sound was heard something like distant 

 thunder, except that it seemed to swell rapidly and steadily to a 

 maximum intensity, and then diminish again in much the same 

 way, but more slowly. I immediately connected the sound with 

 the appearance of the meteor, and stated that it must have been 

 a little over sixty miles distant, and from the estimated angle of 

 elevation about thirty miles above the surface of the earth. This 

 estimate was borne out by the accounts from other places of the 

 course of the meteor. The sound I should be inclined to 

 attribute to the rushing together of the air in the wake of the 

 meteor, or perhaps more probably to the sudden cr mpression of 

 the air in front of it, and not to its bursting. 



The following account of the meteor was given in the 

 Canadian Weather Review of July 1884: — "A magnificent 

 meteor was seen on the night of the 3rd at 8.27 p.m. standard 

 time, passing from south-east to north-west, colours brilliant red 

 and green. Two distinct explosions are reported to have been 

 heard. After the first explosion a sinuous streak remained 

 visible until covered by clouds ; the time of flight was from seven 

 to eight seconds, and the apparent size about one-fourth that of 

 the moon. Reports have been received from Listowel, Hastings, 

 Beatrice, Belleville, Lakefield, Pembroke, Peterborough, Kings- 

 ton, Deseronto, Lindsay, and Huntingdon, all substantially 

 agreeing as to course, size, &c. ; it passed two or three miles 

 south of Belleville, and about the same distance north of 

 Lindsay." Charles Carpmael. 



Toronto, December 16, 1887. 



The Electrification of the Air. 



In writing upon the electrical condition of the Peak of 

 Teneriffe, the Hon. Ralph Abercrombie (Nature, vol. xxxvii. 

 p. 31), begins by stating that "the limited number of observa- 

 tions on atmospheric electricity which have been already made 

 all point, with one exception, to a normal positive difference of 

 potential between a point some few feet above the earth and the 

 ground itself ;" and farther on he writes : " the electrical con- 

 ditions of the Peak of Teneriffe [the one exception] were the 

 same as in every other part of the world." As similar state- 

 ments still find their way into text- books and treatises on 

 electricity and meteorology, I trust you will permit me to point 

 out that, unless a very special m'. aning be attached to the word 

 " normal," this generalization is decidedly too wide. 



In a paper read at the Aberdeen meeting of the British Asso- 

 ciation in 1885 (printed Phil. Mag., November 1885), I pointed 

 out that, in Madras at least, a negative electrification of the air 

 was a normal, and not an abnormal, condition for many hours 

 of the day at certain seasons of the year. Observations since 

 taken have entirely confirmed the opinion that with a hot, dry, 

 west wind the air at Madras is usually negatively electrified, and 

 often to a very high potential. 



With regard to observations made on mountains in the 

 tropics, though perhaps hardly within what Mr. Abercromby 

 terms "the zone of constant electrical discharge," I would 

 venture to call his attention to a short paper on observations 

 made on the top of Dodabetta (8642 feet) in the Transactions of 

 the Royal Society of Edinburgh, vol. xxxii. p. 583. 



I may add that during the periods of incessant discharges of 

 sheet lightning which we often experience here the electrifica- 

 tion of ihe air is sometimes positive and at other times negative, 

 but generally positive. C. MiCHiE Smith. 



Madras Christian College, Madras, December 14, 1887. , 



Wind Force at Sea. 



Prof. Waldo, in the American Meteorological Journal for 

 October, recommends the use of instruments for determining the 

 velocity of the wind at sea. In a paper read before the Meteorologi- 

 cal Society, I discussed the comparative results, obtained from a 

 great number of observations under all conditions at sea, between 

 two very simple and small anemometers, showing that, although 

 the two instruments were on entirely different principles, the 

 results obtained differed only by about 10 per cent. In a paper 

 read in March last before the Meteorological Society, "Notes 

 on taking Observations at Sea, &c.," I again urged the desir- 

 ability of observers using some form of anemometer, so that 

 more uniform results could be obtained, and I gave a table for 

 correcting the apparent velocity of the wind as registered by the 

 instrument for the speed of the ship and for aberration. 



For instance, at the present time you may have two sailing- 

 ships close together, one carrying top-gallant saih, the other only 

 reefed top-sails, and the wind will be logged accordingly. Again, 

 two steamers going in opposite directions are very likely to ex- 

 perience apparently different wind velocities, and the senses of 

 officers in steamers are not so acute for detecting differences in 

 wind velocities as are those of officers in sailing-ships. The use 

 of instruments would eliminate there errors. 



With instruments similar to those I use — the coefficient of 

 friction of which is slight — the relative velocity of the wind may 

 be obtained fairly accurately ; and I contend that this is of more 

 importance than the chance there is of obtaining the estimated 

 true velocity ; and, I may add, the trouble attending the use of 

 these instruments is small. 



There are two other subjects which, up to the present, have 

 received little attention at sea, viz. the registration of rainfall 

 and the electrical condition of the atmosphere. Observations on 

 both could easily be carried out on board some ships, and the 

 observations would be both valuable and interesting. 



David Wilson-Barker. 



A Troublesome Parasite of a Brittle-Starfish. 



In a valuable work on certain parasitic Crustacea (" Contri- 

 butions a I'Etude des Bopyriens," p. 181), Prof. A. Giard and J. 

 Bonnier have done me the honour of calling attention to my dis- 

 covery of a Copepod (?) which lives in the body of an Ophiuran, 

 AmJ-hinra sqiiamata. They regard the mutual relationship of 

 the Copepod and the Ophiuran as an instance of the castra- 

 tion of the host by the parasite. Although all my observations 

 indicate the correctness of some such an interpretation, I failed 

 to recognize it as a fact until after they had pointed it out. The 

 explanation seems a possible one, and is provisionally accepted, 

 with a few modifications, as the best as far as research has gone. 

 The modifications are important. 



The state of knowledge of the subject is as follows. Ova 

 and young of a Crustacean are found in the body of an American 

 brittle-star, identified as Amphiura squamata. In some in- 

 stances an adult Crustacean was also found in the same place. 

 When these ova, young, or adults are found parasitic in the 

 Amphiura, the remains of the ovary of the host appear as an 

 amorphous mass, and there is no possibility of future young 

 of the Amphiura in the brood sac, since the ova have been 

 destroyed. 



The conclusion seems inevitable, for observations indicate that ^ 

 the mother Crustacean makes her way somehow into the body of jj 

 the host (Amphiura), then affects the brittle-star so that the *- 

 young of the host will not develop, after which she leaves 

 packets of ova to mature in the sacs where normally young 

 Amphiurse would develop. It thus happens that the products J| 

 of the ovary of the host are destroyed before the Crustacean ova ^ 

 are developed, or while they are in an early stage of cleavage. 

 Consequently it is legitimate to conclude that if the ova of 

 the host is destroyed it may be done by the adult Crustacean. 



If Prof. Giard and Bonnier are right in their interpretation 

 that this is an instance of parasitic castration, as I think they 

 are, we possibly have an interesting case of a parasite destroy- 

 ing the reproductive powers of the host for the future good oj 

 her own offspring. Such a condition of things is unique, and 

 among Ophiurans the writer recalls but the single instance of 

 the present case of Amphiura. The case of the Crustacean and 

 its brittle star h< st seems to differ from that of Entoniscus in 

 that in the one instance the destruction of the ovary maybe of 

 advantage to the parasite, while in the other the destruction or 



