THE TRANSIT OF VENUS.

New Zealand Herald, Volume XIX, Issue 6571, 8 December 1882, Page 6

THE TRANSIT OF VENUS.

THE UNITED STATES EXPEDITION IN THE DOMAIN. SUCCESSFUL PHOTOGRAPHIC OPERATIONS. This event, for which so many elaborate preparations have been made, and upon which during many years a largo amount of earnest thought has been bestowed, is now a thing of tho past. It may safely be said that there is not a civilized Government in the world but has done more or less to swell the stock of human knowledge in this respect. For years before the transit in 1574 e»rn«st preparations were made to wrest aa much useful information from that event as possible. Unlike the preliminary preparations made m the days of Cook and Horrox, the men who were allotted to do the work of 1874 and 1882 were trained to their work. They wore made to serve as it were an apprenticeship to fit them for the work they undertook. If there is one thing that distinguishes the world .at the present time beyond those of more ancient date, it is by the thoroughness with which everything is done and undertaken. We allude, of course, to scientifle and general educational work, not to the falsifications which crecp into trade practice*. Those who had to do the work of observing in 1874 and 18S- had, as previously stated, to undergo a thorough course of training. An imitative sun was made, an artificial Venus was brought into play, and dozens of observers were made to observe simultaneously the artificial transit thus produced. The results were caretully checked and verified, and this work was gone over again and for months until the observers were tn.ule perfectly familiar with all the phenomena which was to be expected from au actual transit of Venus. The observers of to-day thus entered upon their dutie3 with a certain degree of confidence They knew- what was expected of them, and the way in which they were to use their appliances. Everything that was possible to explain was explained beforehand, and every possible difficulty anticipated and provided against. The improvement of instruments has been carried to the highest pitch of perfection which the science and art of the present day could accomplish, and money has been forthcoming to meet the expense when there was a reasonable prospect of success. Not only was this so in so far as mere observing the contacts of the planet with the edge ot the sun at ingress and egress was concerned, but when the art of photography was applied to the same purpose, men were specially trained for the work. New methods of preparing plates and developing the same have been devised and adopted. And all this trouble has been taken and expense incurred to endeavour to reach as near as possible to absolute truth, so far as the distance of the sun from the earth is concerned. This obtained, would afi'ord a correct guide and measure in estimating the vastnuss of the immensities around us, as well as correcting any errors in the attraction which the sun exercises upon the earth's nearest neighbour —the mo in. We have already alluded to the importance of this work, and the principles of the methods by which such results are sought to be achieved, and at present we need do no more than remark, that unless the question «as .onsidered one of the highest importance, (lurcrninents would not spend sums of money on a matter devoid of all the excitement and glory of cruel war.

It need not be pointed out that however well men might be trained, and however lavish the scale upon which preparations had been made, succe*.i was impossible without the occurrence of favourable weather. That was an element in the success of the work that no money could purchase, or no earthly influence could secure. But now that the transit is past, it is picasant to reflect that a very large measure of success has been achieved, especially in Xew Zealand. Whatever may be the fate of more distant observing parties, those inXc.v Zealand have been really successful, and those in Australia h*vealso had a very fair measure of success. It was important that Auckland should be favoured with good weather, as her easterly position made this station one of very great value. And from what we already know of the general result of the observations in New Zealand, these observations will form subjects for discussion for many years to come, and for more than 121 years the records obtained yesterday will form the standard permanent records of great value which will be referred to again and again during that long lapse of time. How intimately thus will the history of New Zealand become associated with the history of the transits of Venus? In 17G9, Captain Cook was sent to the Society Islands to observe the transit of that year for the British Government. While there he learned that the natives of those islands bad a tradition that there was a large island lying in the direction they pointed—a long way distant. The accounts which Captain Cook heard of the inhabitants made him desirous to know this unknown iiland, and see this strange people. When his work in connection with the observation of Venus was finished he started on his voyage of discovery, and thm broJght the knowledge of the existence of what is now a prosperous British colony before the British people. In due time his second expedition to New Zealand was fitted out, and te-day New Zealand is one of the most prosperous of British coloniei. It was discovered in connection with a transit of Venus which had no successor until after the lapse of over a hundred years, and yesterday the most important data were accumulated in connection with a corresponding event which cannot be superseded for over 121 years. It is strange that the history of New Zealand is so connected with the trausit of this planet between the sun and the earth.

As explained in a previous issue the United States Government sent a large and well equipped party of observers to Auckland undor tile general direction of Mr. I'.dwin Smith, of the United States Coast and Geodetic Survey. Every preparation had been made by Mr. Smith's unceasing care and the unwearied industry of Professor Pritchfitt, to render the observations successful should the weather prove favourable.

When the sun rose yesterday the weather was very unpromising. Heavy masses of clouds rolled about, and many indications existed of a near approach of rain. About half-past five o'clock, however, the sun's rays broke through the clouds, although for some time afterward many light fleecy clouds passsd between the observer and the sun. The American party, however, under Mr. Story, the chief photographer, succeeded in taking good photographs. The exact time each plate waa exposed to the sun was recorded in the chronograph, the slide to admit the sun's rays cutting and reuniting the galvanic connection with the chronograph, which, in the old block-house, silently made the instantaneous record. There were 72 excellent photographs obtained in successive order without a break, but about seven o'clock heavy masses of clouds suddenly rolled up, and photographic operations had to be suspended. For a time those in the dark room wondered what was the cause of such prolonged silence, after the signal had been given to take no more photographs until further ord'er.-s. Professor Pritchett, who waa then ia the photographic: house, waited until at last his patience was worn out; the prepared plates were put past, and the door opened. They were all greatly surprised to see how densely the clouds had covered the sky in so short a time, and it was feared that all furtjier photographic work was at an end. However, a little before the calculated times of contact, the sun broke out again, and two more excellent photographs were secured, thus making in all 74 photographs, each of which is capable of being used for minute measurements. Though Mr. Storey had prepared 150 plates, they were to be quite satisfied if they got 50 good negatives. This is quite a dilferent class of success as compared with that which Mr. Smith's party met with on the Chatham Islands in 1874, when only eight good photographs were got. Professor Peters, in Southland, succeeded in getting in all 90 photographs on that occasion, but a very large number of these of no scientific value, while the 74 got yesterday are all available for the purposes they were intended, micrometric measurements. At the brief period of sun■hine at the times of the internal and external contacts, Mr. Smith observed with the large 5-inch equatorial telescope, while Professor Pritchett used a smaller instrument in the same enclosure. The contacts were clearly ■een by both observers and the time noted, but at the time of our visit yesterday the necessary corrections for chronometrlc variation had not been applied, and the exact local time was not knows. About the befinning of the week the necessary work will e performed to obtain this result. On the evening previous to the time of •beervation Mr. Smith issued the following

instructions to his party as to how they | were to proceed , All members of the party will be at the station at J 4 a.m., and will take tueir stations and perform their duties as directed by tho chief of the party, rhe A"t duty to be performed will bo the testlnjjof the of the photo heliograph, and the measurement of the distance between the buck surface of th° l>ho »_ graphic lens and the front surface of the Reticule plsto. Th««o duties will be performed by the «'»!■''t-ant-astronomer, assisted by Sir. Gamble ; after which he will immediately compare the chronometers and clock. The duties of tho various members of the nartv will then bo as follows: The caief of party will take charge of tho operations in the photographic house. The assistant-astronomer willtake charge of all operations outside the photographic house : will see that the heliostat and chronograph are properly care "for and will measure tho diameter of Venus with the double-image micrometer on the Lquar, -ivLscooe No. 881, at such intervals as ho ■en* fit flalf-an-hour fcefore contact he will take off tho double - iuiace micrometer, and put an the eye-piece for observing contact. The heliostat will be in charge of Mr. Gamble ; whenever he is to adiust the heliostat ho will make two snort rings of the bell »nd on completion of the adjustment will make one rlr.i:. In case of a passing cloud obscuring the sun he will make one lone ring of two or thrao seconds' which will Udicate to those in th» photographic house that no more exposures are to be made uitil the adjustment slinal is again heard. Incase the lusis in a thin cloud, so that a very slow exposure has to bo made, ho will make four or live short rings, and wlisn the aim is out of the cloud, he will indtcato it by one short rins- The chronograph will bo wound and supplied with ink ky Veanison. Shields Mill be on duty inside the enclosure for any purpose ho mar be required. In the photographic house the cliitf photo.THuhor will remove tho plates from the box, placo them in the holder, call o.it .lir number, and after the exposure. will pi-'S them to the assistant photographer for doveinpm rt nt, or "lit them in tho box prepared to receive them. Tho assistant photoxrapher will devolop plates as fast as possible. Tile exposures will I)- m ide an J record kept by tho chief *f ! 1 '*rVy. No mo but tho chief of party, astronomer, a*(l the two photographers will be allowed in photographic liouso on diy of transit In can of a perfectly clear morning, the photographic ope atioti9 "ill begin a'iout five o'clock, when pictures will be taken from three to (We minutes apart, this interval bcinff gradually diminished, and betwe-n six and Sevan tho gre itest number of pictures will bo taken. I;i case tho weather Is not dear, pictures will l>e takea rapidh and whenever possible. About ten "r llfteen mi utes before contict, photographic operations will he suspended, and tho chief photo.raphor will leave the photographic house to record for the assistant a-tronoinerwhiio observing contact, and Mr. Qamble will record for chief of p.rty while olis.i ving cjnt ict. Sidereal chronometer IS. and ii., will be used in tko photographic house and will bo in c rcilit and record on tho chronograph, and will afterwards be used by chief of party in observing contacts. Meantime chronometer 1-14S), will b" used by a-isistmt astronomer. After contacts aro observed, t!ie assistant astronomer will again measuro distance, sidereal chronometer Negus, is not to bo removed from its present position. Any other obs :rvers who may be upon tho ground must furnish their own chronometers or use their watches, comparing tlielll frequently with the moan time chronometer, 1449. Between the two contact observations no communication regarding the nature or time of tho tlrst of the two contacts is to take place between tho observers. All notos and records must be completed before the observers leave the station. Th* chronometers and clock are again to bo compared very soon after tin: transit, is over. In case the chief of partv is unable to perform tho duties assigned to him above, bis placo will be tilled by the assistant astronomer. 11l this c tso the measurement of the diameter of Venus may bo neglected, and lie must mako somo arrangement by which he will be rottain of the chronograph rocord.—Edwin Smith, Chief of Party.

The duties, as detailed in the above instructions, were duly carried out, with the results we have stated. Mr. Story, the chief photographer, and his assistant, Mr. Theilkuhl, are quite pleased with the measure of success which has fallen to their share of the duties. The only persons inside the enclosure at the time the observations were made were Mr. J. T. Stephenson, who observed with a large reflecting telescope, Mr. Gamble, Acting American Consul, Mr. 11. P. Barber, and Mr. .Tames Coates. A considerable number ot people

gathered outside the enclosure, and seemed to take a oonsideraMe interest in watching the various observations. Of course it will be several years before the data collectcd yesterday are so reduced as to give the inlormation sought, but nil must feel pleasure to know that tho success of tho American party of Observers at Auckland has been greater than they anticipated, and compares so very favourably with the results by the Americans ia 1574. The American observers saw nothing of the " black drop." nor any unusual appearance about Venus at all. PROFESSOR LAMBERTS OBSERVATIONS. It must be highly satisfactory to all concerned in the transit of to-day, so far as the colonies are concerned, to have been privileged with such lino weather for their operations. Those who were to have taken part in the transit of 1574 will remember the disappointment they suffered owing to bad weather ; but it must be gratifying to such as are still in this part of the world, that the only opportunity possible to them in this respect, proved so favourable for them to see Venus on the sun's disc. Our place for observation was ou a rising piece of land in the New North-road, belonging to Mr. Stuart, commanding a good horizon at sunrise. Our instruments consisted of one 3-incli, and one 2-i-ineh telescopes, and one instrument fitted up for photographing the transit. To the care of' Mr. Stuart, jun., the latter was allotted. Mr. Stuart possesses much skill both as an astronomer and as a photographer, and to him much of the task fell in fitting up the various instruments for use. My own department lay chiefly in telescopic observations. The first sight of Venus was obtained by the naked eye, when the sun had but partly risen, after which, for some time, the sun shone through a hazy formation of cloud, which gradually cleared away. As soon as the sun had sufficient altitude, wo commenced to take photographs, but very soon a cloud put an end to this operation. However. a good series of photographs wrs obtained before the commencement of any interference. Before the clouds came up Venus was closely examined through the telescopes, but notliinc peculiar was noticed, exeept a faint ring of light surrounding the pianet, which was more intense when viewed through this intervening aloud ; but no traces of anything appertaining to a satellite was recorded. Both Mr. Stuart and myself observed the internal contact at egress, but no trace of a " black drop" was saen by either of us. The photographic method we used w»b that known as the wet-plate as re•ommended by eminent authorities in England, and the lense used for this purpose was by Dallymier. Of course tho final results of all these observations will take much time to discuss, and will probobly not be known for some years. S. J. Lambert, F.R.A.S.

CAPTAIN HHALli'rj OBSERVATION. Captain Heale's observations were carried out by him iu the observatory which he has had erected near hi? dwelling at the extreme end of St. Stephen's Avenue, Parnell. The instrument he has in use is that imported by Messrs. Porter and Co. some time ago, and which was lent for the occasion. The instrument was carefully mounted on a brick pedestal, and Captain lteale considers it a very excellent one. He took observations of 10 stars prior to the rising of the sun, and worked out ths calculations in order to make certain of the perfcct accuracy of his chronometer. The last contact, according to Captain Heale's observation, was a fraction of a second after eight o'clock, Auckland mean time, but this is Omins. and about lOsecs. ahead of New Zealand time. The following is his report of his observations : — " The planet was visible on the sun's disc plainly enough through thin, low, misty clouds, upon sun rise, until about a quarter past seven. Tho unit then thickened, and I saw nothing of the internal contact of the limbs ; but a few minutes later it partially cleared, so as to afford .a very good view iu tke telescope without tile use of a coloured wedge. The body of the planet was perfectly well defined, without tho least distortion, and tho cusps perfectly sharp. The external contact was, therefore, observed with the greatest accuracy. The previous night was perfect for star observation, and irave every opportunity of obtaining an accurate clock error, and the meridian transit of the suu, which I also took, leaves the accuracy of the chronometer beyond doubt." MR. J. T. STEVENSON'S OBSERVATIONS. From an early hour the sky was earnestly scrutinized for signs of good weathor yesterday, and when the sun rose at Auckland at 7hrs. 4lmius., it was hoped that the light clouds then covering the sky would soon be dissolved by tho sun's heat. Towards the end of the transit, however, the clouds again came over the sun, which up to 6.30 a.m. had been nearly cloudless from this time up to near internal contact, the sun was seen with difficulty. In transit, Venus appeared of a greyish brown hue. At 4"urs. 45mim., a few minutes after sunrise, she could be seen by the naked eye, without any shield from the solar glare. There was no appearance of any atmosphere surrounding the planet. Tho disc appeared porfeotly circular, and of a uniform colour, which, when the eya became more accustomed to the solar glare, assumed a darker hue. At 19hrs. 41mins. Msec., Auckland meridian time, but which ia subject to slight correction, tho first interna 1 contact took place. The sun, being covered with clouds, made tho observation of this phaso not bo acourate as it would otherwise hare bean. There

was no appearance of the black drop observed, neither was there any appearanee of the light surrounding the limb of the planet which observers at previous transits hare seen* This, however, may be owing to the clouds by which the body of the sun was covered. Probably had the iisc been claar, some phenomena of the above nature might have been seen. At 7hrs. SOmins. 30secs. it was estimated that Venus was half-way across the limb. At Shrs. •mins. 4see3. the last external contact was r«corded. The preceding times are all subject to slight correction for difference of chronometers. Tho last contact was made with greater exactness, as the sun at this time was comparatively free from cloud. MR. THOMAS CHEESEMAN'S OBSERVATIONS. As our'readers are well aware, Mr. Thomas Cheeseman, senr., Retnuera, has a large reflecting telescope. This was uied yesterday at his residence, Remuera, but not for scientific purposes. The times of contact were not carefully noted, nor were any efforts made to ascertain true time, or the exact longitude of the place where the instrument wai used. Tke whole course of the transit, except when obscured by clouds, was clearly seen, and as the time for internal contact approached it appeared to Mr. Ch<!eseman as if the outer edge of the sun was bulged out a little just before the contact was actual. The phenomenon may have various explanations, but the more reasonable is pr*bably that as Venus neared the sun's edge the glowing light behind the dark body of the planet shone through the dense atmosphere of Venus, and thus appeared to swell the illuminated edge iu front of the dark body of the planet. OTAHUHU. ;; From sunrise to 6 a.m., the weather here was hazy, but clear at intervals ; after 6 o'clock, it became more cloudy until near 7, when the light clouds cleared away, and the transit was visiblo without interruption to the end. As well as one could see with an imperfect glass, the " black drop " was not visible, although between the times of the internal and external contacts of egre9s, the round form of the planet apparently lengthened to a somewhat oval or egg-like shape. Tonus disappeared from tho outer edge of the -un's disc about 7.47 Auckland time.