July 20, 1893] 



NATURE 



27; 



The observed and calculated positions agree only in the limits of 

 the errors of observations on the assumption "of a periodic term, 

 the period of which is nearly identical with that of the lunar 

 period, and whose maxima and minima occur at epochs when 

 the longitude of the moon differs by 90° from that of the planet. 

 Adopting 6"-40 in place of 6"'5o for the lunar equation, the 

 residuals obtained from the corrected ephemeris and the ob- 

 servations are made very small, as can be seen from the last two 

 columns of the above table. 



The correction of — o"l in the lunar equation demonstrates, 

 as Dr. Gill says, that the value adopted up to the present for the 

 lunar mass ought to be diminished by one-hundredth. 



Difference of Longitude between Vienna and Green- 

 wich. — In the fourth volume of the " Publicationem fiir die 

 Internationale Erdmessung," entitled " Astronomische Arbeiten 

 des k.k. Gradmessungs-Bureau," by Theodor v. Oppolzer, and 

 after his death by Prof. Weiss and Dr. Robert Schram, we are 

 presented with the results of the determination of the difference 

 of longitude between Vienna and Greenwich, and with the 

 Berlin time determinations and the personal equations of the 

 separate observers relating to other longitude determinations, 

 those between Vienna — Berlin — Munchen — Greenwich. We 

 may mention here that, with regard to the first-mentioned de- 

 termination, another one, between the same places but after a 

 method due to DoUen, by observations in the vertical of Polaris, 

 will appear in a later volume. 



The observations for the combined longitude determination 

 between the above-mentioned places were commenced on July 

 7, 1876, and were completed on September 26 of the same 

 year. Not only was the usual method of procedure adopted, 

 but also that which we owe to Dollen, the instruments used 

 being, for the former method those by Repsold, and for the 

 latter those by Herbst. In the Vienna— Greenwich longitude 

 determination at the beginning and at the end of the observa- 

 tions, time signals, both from Vienna and from Greenwich, 

 were changed with Berlin ; in the middle observations Vienna 

 — Greenwich interchanged time signals ; and towards the end 

 Miinchen was included. In the following table, which gives 

 the results for the single evenings, AL represents the longitude 

 between the points of observation and (ML the deviations from 

 the most probable value of the longitude difference : — 



Date. AL. dW. 



h. m. s. s. 



17 July, 1876 ... 1521-037 ... -fo-043 



21 ,, ... 21'028 -(-0034 



22 ,, ... 20995 ■ • -l-O'ooi 



26 „ ... 20-955 ■•• -0039 

 5 Aug. ... 20-832 ... - 0-162 

 7 ,, ... 21-107 •■■ +0-II3 



17 ,, ... 21 146 ... -HO-I52 



21 ,, ... 20-845 ■•• -0-149 



27 ,, ... 21016 ... -I-0-022 



S Sept. ... 21 037 ... 4-0-043 



It ,, ... 21 025 ... -f 0-03 1 



21 ,, ... I 5 20-902 ... -0-092 



The result obtained, when the points of observations are 

 reduced respectively to the centre of the Greenwich Transit 

 Circle and to the centre of the large dome of the Vienna Ob- 

 servatory is 



ih. 5m. 2I-42IS. ±o-02is. 



Photographs of the Milky Way.— Prof E. E. Barnard, 

 who has recently been on a visit to Europe, has brought 

 with him some wonderful photographs of the Milky Way, 

 which are simply a revelation to many of us. These photo- 

 graphs (The Observatory, No. 203) were taken at the Lick 

 Observatory with a lens made by Mr. Willard of New York 

 in 1859, which is one of large aperture (6 inches) and short 

 focus (31 inches). Such a lens tends to compress as well as 

 intensify the characteristic features of these stellar clouds, the 

 large field allowing one to embrace any of these forms as a 

 whole, and not in detail, as is the case when they are viewed 

 with a telescope. The first photographs, showing the cloud 

 forms, were taken in August of 1890, the portion of the sky 

 being that situated in Sagittarius, and the exposure 3h. 15m. 

 A most interesting picture is that of a section of the constella- 

 tion of Cygnus, near 7 Cygni ; this photograph shows some of 

 those curious and almost weird dark spots and dark lanes the 

 origins of which are very doubtful. Mr. Ranyard supposes 

 them to be due to an obscuring medium between us and that 



NO. 1238, VOL. 48] 



part of the Milky Way, but Prof. Barnard's opinion is 

 that they are real holes in the cloud structures themselves. 

 Two photographs with different lengths of exposures (2h. 

 45m. and 4h. 30m.) of the region about M. 11 in the 

 constellation of Sobeski raises an important point as re- 

 gards the different structure of the Milky Way. The second 

 picture exhibits details which considerably altered the con- 

 figuration, not at all brought out in the first one. Not only in 

 these photographs, but in several others of the Milky Way, this 

 fact has been noticed, and Prof. Barnard suggests that there may 

 be different orders or kinds of cloud structure implying distance 

 or nearness, or possibly an entirely different order of stars in 

 point of actual size. 



THE 



INSTITUTION OF 

 ARCHITECTS. 



NAVAL 



'T'HE summer meeting of the Institution of Naval Architects 

 -•■ was held last week in Cardiff. This is only the fifth pro- 

 vincial meeting held by this Society since its foundation. The 

 first was in Glasgow, the next in Liverpool, and the third in 

 Newcastle. The fourth was held again in Glasgow. All the^e 

 meetings were eminently successful, and it is somewat strange 

 that the Council should not have made a point of holding a 

 country meeting every year. We believe, however, that it is 

 now the intention to follow that course, and certainly the great 

 success of the meeting held in South Wales last week will sup- 

 port those who advocate two meetings a year. 



We propose in our report dealing only with the sittings held 

 for the reading and discussion of papers, but it may be stated 

 that the excursions were very successful. Some of these were 

 of a purely recreative nature, such for instance as that which 

 occupied the whole of the last day, Friday, the 14th inst., when 

 members were taken from Cardiff to Illracombe and back by 

 the steamer Lor/ia Doonc. The visit to Caerphilly Castle, 

 with the luncheon in the ancient banqueting hall, could not 

 by any means be construed as " business" for naval architects, 

 and the same might be said of the visit to Lord Windsor's 

 grounds at Penarth, illuminated for the occasion. 



Mixed with these junkettings, however, there was a good deal 

 of a more serious nature, as the following list of papers read, 

 will show : — 



(1) " On points of interest in the construction and repair of 

 vessels carrying oil in bulk," by B. Martell, chief-surveyor of 

 Lloyd's Registry of Shipping. 



(2) " On fast ocean steamships," by F. Elgar. 



(3) Some experiments on the combination of induced draught 

 and shot air, applied to marine boilers fitted with serve tunes 

 and retarders," by J. D. Ellis. 



(4) " On wear and tear in ballast tanks," by A. K. Hamilton, 

 of Lloyd's Registry. 



(5) " On the transmission of heat through boilerplates,' by 

 A. Blechynden, Barrow. 



(6) "On water tube boilers," by J. T. Milton, chief-engineer- 

 surveyor to Lloyd's Registry. 



(7) "On the theory of thin plating and its applicability to 

 calculations of the strength of bulkhead plating and similar 

 structures," by G. H. Bryan, of Cambridge. 



The last paper was not read, but distributed at the meeting, 

 the discussion being deferred until the spring meeting of next 

 year. 



On the members assembling at the Town Hall, Cardiff, on 

 the morning of Tuesday, ihe nth inst., they were welcomed by 

 the Mayor of Cardiff, and the chair was then taken by Sir 

 Nathaniel Barnaby (late Director of Naval Construction), the 

 President, Lord Brassey, not having arrived. Mr. Martell's 

 paper dealt with various details involved in the construction of 

 oil tank steamers. It would seem at first sight a simple matter 

 to construct a steel vessel capable of carrying oil in bulk ; 

 but this is by no means the case, and in trying to solve the 

 problem involved naval aichitecis have been met by some alto- 

 gether novel problems. One of these is the arrangement of 

 riveting, and with ihis feature ihe author dealt at some length, 

 going into details in the ihorough manner which his unique posi- 

 tion enabled him to do. Without diagrams it would be im- 

 possible to follow the author in his various lines of reasoning, 

 more especially in the matter of arrangement of tanks, the dis- 

 position of stringers, brackets, and other parts of a ship's struc- 

 ture. We will therefore refer those of our readers interested in 



