366 



NA TURE 



{March ii, 1875 



world, had been the scene of operations, and the results, 

 though not all that could be desired, are nevertheless well 

 worthy of the time and money expended in obtaining 

 them. 



M. Andre, of the Paris Observatory, a well-known 

 French astronomer, was appointed director of the expe- 

 dition, whilst to M. Angot, Professor of Physics in the 

 Normal School, Paris, the photographic portion of the 

 work was entrusted. The instruments to be used con- 

 sisted of five telescopes of various powers ; a veiy complete 

 photographic apparatus which will be described hereafter ; 

 a meridian instrument ; an apparatus for producing an 

 artificial transit, with electric chronograph carrying four 

 pens attached ; and lastly, two instruments for accurately 

 determining the magnetic inclination and declination of 

 Noumea, which up to the present time have never been 

 exactly known. The largest of the telescopes (yj in.), 

 as well as three others (5 in.), was provided wiili an 

 objective silvered by I\I. Foucault's process, the fifth 

 having an unsilvered kns of 3J in. diameter, and of 

 extremely good definition. All the instruments were 

 equatorially mounted, three of them being connected with 

 the chronograph, whilst the other two obtained their time 

 by means of clock and chronometer. The telescope used 

 for the photographic part of the work had an objective of 

 5 in. diameter and 13 ft. focal length, and was firmly 

 fixed in a horizontal position on stone pillars, the image 

 of the sun being directed along the axis by a large sil- 

 vered mirror pbced outside and moved at will from the 

 interior by means of long wooden rods on either side of and 

 parallel to the telescope. During the transit an assistant 

 stood near this mirror, and at every command " Dc- 

 lOiivicc," removed the cover (placed on the mirror to pre- 

 vent it becoming heated, and thereby causing distortion 

 of the sun's image), and replaced it immediately after the 

 plate had been exposed. With this apparatus, the 

 daguerreotype process of sensitising a silvered plate of 

 copper by means ol iodine and bromine, developing in a 

 mercury bath and fixing with hyposulphite of soda, was 

 alone employed, and with the greatest success. 



Though the day was somewhat cloudy, considerably 

 over 100 very well-defined pictures of Venus during the 

 Transit were obtained, together with 130 others, rendered 

 less distinct by the intervention of clouds. When it is 

 known that for several days previous to the 9th, the 

 weather had been so bad that all hopes even of a glimpse 

 of the transit of the planet were abandoned, and that 

 dense clouds hung over the whole sky, and heavy showers 

 of rain fell up to within four hours of the first contact, 

 M. Angot may well be congratulated on the success of his 

 labours. These daguerreotype pictures are not quite 

 1.' in. in diameter, and weie obtained by exposures 

 ol" the plates varying from yjjj to t;o of a second in 

 duration. M. Janssen's method was not employed, but a 

 very simple plan was adopted of placing the sensitised 

 plate in a frame fixed at the focus of the chemical rays, 

 and causing the exposure by sliding in front of it a 

 metallic screen with a slit in it, whose width of course 

 varied with the time necessary for exposure. A clock 

 connected electrically with the sidereal one in the main 

 observatory was placed in a convenient position above 

 the telescope, and the instant of each exposure accurately 

 noted. The assistants in this work, four in number, were 

 all convicts, who performed their share with the neatness 

 and readiness for which Frenchmen, whatever their posi- 

 tion in life may be, are so remarkable ; and, indeed, 

 nothing has struck me more during the progress of the 

 work here than the aptitude which seems innate in the 

 French race for work of this kind ; and it is no disparage- 

 ment to English soldiers to say that it would have taken 

 them days to learn to read chronometers with the accu- 

 racy which their French brethren- in-arms acquired in a 

 few hours and apparently without the slightest difficulty. 

 The main features in all the telescopic observations are the 



3| minutes' difference between the estimated and observed 

 times of first contact, the absence of the drop, and, in the 

 case of the instruments furnished with silvered objectives, 

 the clear tangential contact of the planet and the sun's 

 hmb, which enabled four out of the five observers to 

 obtain the instant of second contact with very great accu- 

 racy. With these objectives, which appear to be espe- 

 cially well adapted for observations of this nature, the 

 planet was seen to pass clear and distinct on to the sun's 

 disc, without any appearance of distortion or cloudiness 

 whatever ; but with the unsilvered objective an appearance 

 was observed as if a drop, such as those described by 

 English astronomers, was about to form. Without forming, 

 however, it changed almost imperceptibly into a tremulous 

 haziness, which rendered it impossible to say when the 

 actual contact took place, and compelled the observer to 

 note two instants, one when this haziness first appeared, 

 and the other when it had so far disappeared in the 

 increasing brightness in the rear of the planet that he 

 was confident that Venus was fairly on the solar disc. 

 These two instants are separated by an interval of thirty- 

 four seconds, and their mean corresponds within two or 

 three seconds with the instant of tangential contact 

 observed with the other instruments. Whether the slight 

 cloudiness of the sky, or a constant error peculiar to all 

 unsilvered objectives, or the fact that the latter telescope 

 was focussed on a spot much nearer to the sun's limb 

 than the other instruments, is to be put down as the 

 cause of this difference or not, seems at present a matter 

 of doubt only to be cleared up when other observations 

 with unsilvered lenses are recorded. 



The third and most important contact in New Cale- 

 donia was not observed, owing to a cloud which, much to 

 our chagrin, strayed over the sun's face some 6' before the 

 estimated time of egress, and completely shut out our 

 view for about 20', after which the fourth contact was 

 obsetved, but with a considerable degree of uncertainty, 

 on account of the undulatory appearance of the sun's limb. 



I may mention, in conclusion, that the times of duration 

 of the whole transit, i c. the interval between the first 

 and fourth contacts, obtained by three of the observers, 

 differed by only 8", but these were considerably at variance 

 with the estimated duration of the transit as given in the 

 Nautical Aliiianac. Besides MM. Andre and Angot, 

 three French officers, Capts. Dcrbc's, Bertin, Ribout, and 

 Mr. Abbay, took part in the observations. A. 



On board the Kangatira, 

 Jan. 5, 1S75 



SCIENTIFIC REPORT OF THE AUSTRO-HUN- 

 GARIAN NORTH POLAR EXPEDITION OF 

 1872-74* 

 'T'HE real object of the expedition was not particularly tliat of 

 ■*■ reaching higli latitudes, but rather tlie investigation of tlie 

 large unknown sea north of Siberia ; the explorers thought they 

 might eventually reach Beliring's Straits, without cherishing very 

 sanguine hopes on this point. Wlien during 1S71 Lieut. Wey- 

 precht made a preliminary expedition into those regions, he 

 found the whole large sea between East Spitzbeigen and Nowaja 

 Semija so completely unknow-n, that in spite of )iis stopping six 

 weeks at Tromso, and making inquiries of all Finnmark skip- 

 pers and whalers, he could not learn anything definite as to 

 the conditions of climate and ice in tliose parts ; few vessels 

 had succeeded in reaching the 76th degree of north latitude. 

 During the two Austrian expeditions this unknown sea has 

 been investigated from 40° to 70° East long, (from Green- 

 wich), and beyond the 79th degi'ee of latitude on the w-esfside 

 and the Sotli on the east side ; an extensive, hitherto unknown 

 tract of laud has been discovered, and Lieut. Julius Payer has 

 made sledge journeys into this land, reaching very nearly 83° 

 N. lat. 



In I $7 1 the explorers had found the sea completely free from 



* Die 2. Oestcrr.-Ungarische Nord Pobr Expedition unter Weyprecht 

 und Payer, 1872-74, (Petermann's Geogr. Mittheilungen, 1875 ; heft ii.) 



