February 8, 1894] 



NATURE 



S41 



has since shown ^ that the increased density of the jet on elec- 

 trification is only partly due to the cause to which I attribute it, 

 namely, the electrical repulsion preventing the coalescence of 

 the drops, as he proves that the electrification of the jet over- 

 powers the surface tension, and so promotes the formation of 

 small drops, and in this way assists in increasing the density of 

 the condensation. 



Mr. Bidwell's misunderstanding of my position is greatly due 

 to an impression he seems to have that I attribute all cloudy 

 condensation to the presence of dust particles. Now, if he will 

 turn to my first paper on this subject,- he will find that the 

 effect of the vapours of hydrochloric, sulphuric, and nitric acids, 

 active vapours, mentioned in his lecture, have all been referred 

 to, and experimented with, as well as many other substances, 

 so that I was well aware of these causes of condensation. 

 Further, he will find in the paper referred to, as well as in 

 another of a later date,^ that it is possible to produce cloudy 

 condensation without the presence either of dust or a vapour 

 capable of forming a nucleus with water vapour, or even the 

 abnormal condition due to electrification, all that is necessary 

 being a sufficiently high degree of supersaturation. 



Darroch, Falkirk. JOHN AlTKEN. 



The Os Pedis in Ungulates. 



Prof. Ewart, in a recent paper,^ describes the os pedis or 

 " coffin bone " of the horse as consisting to a large extent of a 

 bony cap developed from connective tissue around, and quite 

 independent of the terminal phalanx. This throws an entirely 

 new light on one of the most remarkable bones of the horse's 

 skeleton, and ic especially interesting to veterinarians. Having 

 a foetal calf (about 6| months) in my possession, I was led, on 

 reading Ewart's paper, to examine the digits, and wish now, in 

 a word, to state the result. 



I found each digit provided with a bony cap similar to that 

 figured by Ewart from his 35 cm. horse embryo. On making 

 a longitudinal vertical section of one of the digits, the investing 

 cap could easily be distinguished from the phalanx proper ; 

 and, further, I noticed a large deposit of osseous matter in what 

 may be termed the diaphysis (shaft) of the terminal phalanx, 

 and an indication of a second ossific centre at its apex. This 

 affords additional proof that the third phalanx in ungulates, as 

 in man, consists partly of membrane bone and partly of 

 cartilage bone, and that it in all probability develops from 

 several centres. 



I hope soon to publish a number of observations on the 

 structure and development of the digits in ungulates. 



A. E. Mettam. 



Royal Veterinary College, Edinburgh. 



A Brilliant Meteor. 



A METEOR of extraordinary splendour was seen here this even- 

 ing at 7.45. It appeared vertically under the Pole star, at an 

 elevation of 40^, and, after pursuing a path that sloped down to 

 the west at an angle of 30°, disappeared silently under Cas- 

 siopeia. 



The incandescent mass had an apparent volume equal to that 

 of a good-sized orange. It gave out a bluish-white light that 

 brilliantly lit up, for about four seconds, the grounds and build- 

 ings of the College. 



The glowing mass was followed by a long, conical, crimson 

 train ending in a wisp of condensed vapour resembling smoke. 



The sky was clear, starlit, and moonless at the time. 



M. F. O'Reilly. 



The Training College, Waterford, January 31. 



THE VA TIC AN OBSER VA TOR Y. 

 T^HE report recently issued by the Vatican Observatory 

 -*■ {Pubdlicasiom della Specola Vaticana, Fasciculus 

 iii.) is the best that has been prepared by Father Denza, 

 and in abundance of matter and fineness of execution, it 

 compares favourably with that of any observatory. The 



i Phil. Mag-. October, 1893. 



3 ''Dust, Fogs, and Clouds." {Trans. Roy. See. Edin., vol. xxx. part i.) 



3 ' On the Numbers of Dust Particles in the Atmosphere." (Trans. V^oy- 

 Soc. Edin. vol. .\xxv. part i.) 



4 "The Development of the Skeleton of the Limbs of the Horse." 

 {Journal of Atiatoviy atui Physiology, January, 1894.) 



NO. J 267, VOL. 49] 



first report was published in 1891, but neither that nor 

 the one of 1892 contains so much evidence of work done 

 as the bulky tome last issued. The observatory, as it is 

 at present constituted, only dates back to 1889 ; but pre- 

 vious to that, it passed through so many vicissitudes that 

 a brief outline of its history may be of interest. 



It is recorded that an observatory tower was erected 

 by Pope Gregory XIII. in connection with the reform of 

 the calendar, some time previous to 1582. The tower 

 was intended for astronomical observation, and there is 

 every reason to suppose it was the first celestial watch- 

 tower built in Rome. The following translation of an 

 e.xtract from the Aateiica Mcditcrranea of B. Crescenzi, 

 published in Rome in 1607, clearly shows that the room 

 at the top of the tower was used for astronomical pur- 

 poses :■ — " When the sun arrives at the tropic of Cancer 

 its rays enter a little hole which Ignatius Danti has had 

 made for that purpose in the roof of the apartment which 

 Pope Gregory XIII. had erected upon the Belvedere Gal- 

 lery, and the rays only enter the hole once a year, when 

 the sun is furthest from the equinox, after which he turns 

 and goes back." Danti appears to have marked a 

 meridian line upon a marble table in the tower, and 

 meridian observations were made until about 1644, 

 but the observatory was afterwards neglected, and 

 remained so for about a century and a half. It was 

 only towards the end of the last century that an attempt 

 was made to renew the astronomical work. Cardinal 

 Zelada had a large meridian circle constructed, and fur- 

 nished the observatory with some good astronomical 

 instruments, among which was a telescope by DoUond. 

 As the observatory was not available for public instruc- 

 tion, it was decided to establish another at the Roman 

 College, and the new observatory was erected in 1787, 

 though observations had 'oeen carried on at the College 

 long before. 



In 1789 the Vatican Observatory commenced a new 

 epoch in its history. Philip Gili began his directorship 

 in that year, and, in addition to making astronomical 

 observations, initiated researches in magnetism and 

 meteorology, and other branches of terrestrial physics. 

 The observatory kept well apace with the times until the 

 death of Gili in 1821, but after that it became quite dis- 

 organised. All the instruments and records were dis- 

 persed, and the observatory itself was entirely deserted 

 until about 1870, when it was transformed into a 

 residence. 



Before passing to the third epoch in the " eventful 

 history " of the Vatican Observatory, a few remarks 

 upon the Observatory of the Roman College may be of 

 interest, especially as the relations between the two 

 institutions are not generally well understood among 

 astronomers. According to Father Cortie, who has 

 kindly furnished most of the following information 

 upon this matter, the Roman College Observatory 

 dates back at least to 1572. It belonged to the 

 Society of Jesus, and consisted in the beginning of 

 a few rooms set aside for astronomical studies. 

 Scheiner, of sun-spot fame, Clavius, the author of the 

 Gregorian reform of the calendar and the observer of 

 Tycho Brahe's Nova of 1572, de Gottingues, who ob- 

 served Jupiter's spots and the comets of 1664, 1665, and 

 1668, Boscovich, and other renowned astronomers were 

 connected with it. There still exists in the Kircher 

 Museum of the College a meridian line traced by 

 Boscovich, and the same astronomer drew up the plans 

 for a new observatory, but they were never carried into 

 effect, on account of the troubles in France and Spain, 

 during which the Society of Jesus was suppressed. 

 During the period of the suppression, the observatory 

 was directed at first by J. Callandrelli, who in 1773 built 

 a square tower at the eastern angle of the facade of the 

 College, and placed in it a zenith-sector and a meridian 

 circle, the gifts of Cardinal Zelada and Pope Pius VII. 



