July 20, 1876] 



NATURE 



257 



alone. There are several kindred processes worked at present, 

 amongst which I must notice that of the Autotype Company. In 

 their process an exceedingly thin layer of gelatine is formed on 

 the plate and hardened by means of gum resins. The gelatine is 

 not removed from the plate, but it is printed from whilst still on 

 it. The film is hardened, from the back. The glass plate can be 

 inked in as described for the heliotype process, and can be pulled 

 in a lithographic press or in an ordinary printing-press. M. Thiel, 

 of whose process we have beautiful examples on the walls of this 

 room, uses an ordinary lithographic printing-press. 



I have only been enabled to give you a brief outline of these 

 few processes, specimens of all of which are to be found in 

 this exhibition. Short as have been the descriptions, I hope, 

 however, that they have been sufficient to enable you to see the 

 immense strides in the methods of producing prints that have 

 been made in the last dozen years. When we consider that the 

 autotype, the Woodbury type, and all the other mechanical 

 printing processes have been worked out in that time, you will 

 see that the inventive faculties of those who labour in the art- 

 science have not been allowed to lie dormant. Perhaps in no 

 other occupation is there such a field for discovery and improve- 

 ment as in photography ; and considering the many workers in it, 

 and the large industry it represents, we may surely hope that in 

 1886 we may again be able to record a still further advance ; 

 it may be, perhaps, in the line I have already indicated, and in 

 colour pictures. 



OUR ASTRONOMICAL COLUMN 



The Comet of 1686. — This comet, so far as the Euro- 

 pean observations are concerned, offers a very similar case 

 to that of the comet of 1533, for which two totally different 

 orbits have long appeared in our catalogues. As regards 

 the latter, it was shown by Olbers that ^the observations of 

 Apian between July 18 and 25 were insufficient to decide 

 whether the true direction of motion was in the order of 

 signs or the opposite, the node at the commencement of Leo 

 or the end of Capricornus, or the perihelion in Cancer or 

 in Scorpio ; but the publication of the Chinese observations 

 since Olbers wrote, has afforded evidence which tends to 

 give the preference to his direct orbit, as already intimated 

 in this column. The best observations of the comet of 

 1686, are those of Pere Richaud at Pau, on four mornings 

 between September 7 and 15 ; from his positions for the 

 7th, loth, and 15th, the following orbit was obtained, and 

 for the sake of comparison HaJley's orbit, the only one 

 previously computed, is copied. 



New Orbit. Halley's Orbit. 

 Perihelion Passage, G.M.T. ...Sept. 19*2046 ... Sept. 166063 



Long, of Perihelion 23? 35'-4 ... 77°o'-5 



,, Ascending Node ... 14913-2 ... 350347 



Inclination 3210-1 ... 31 21-7 



Log. Perihelion Distance 9-48730... 9-51188 



Motion. Retrograde. Direct. 



If we compare these two sets of elements with Richaud's 

 places, we find the differences between calculation and 

 observation to be, for i6h. Paris M.T., as assumed time — 



Sept. 



So that from these eight days' observations only it would 

 be difficult to give a decided preference to either orbit. 

 But it fortunately happened that before the comet was 

 seen in Europe, it had been a very conspicuous object in 

 more southern latitudes ; at Para, in Brazil, it had been 

 observed during the whole month of August, the nucleus 

 as bright as stars of the first magnitude, with a tail 18° in 

 length ; in Siam by the French Jesuit missioniiries, who 

 fixed its position approximately between August 17 and 

 23, and at Amboyna on August 15, a little south of the 

 belt of Orion. 



On comparing the two orbits with the Siam observations, 

 it is at once evident that they decide in favour of Halley's 



elements, and on making a further calculation in which 

 the August positions, which are only rough ones, are 

 introduced, the following orbit finally results : — 



Perihelion Passage, 1686, September 15-8249 G.M.T. 



Longitude of Perihelion 75 58-4 ) Equinox 



,, Ascending Node ... 354 3-8 j of 1686. 



Inclination 34 55-7 



Log. Perihelion Distance 9*52636 



Motion . . . Direct. 



On the morning of August 17 the comet was distant from 

 the earth 0*316, and at the time of Richaud's last observa- 

 tion, 0-973. 



While writing on a cometary subject, we are reminded 

 of what appears to be an unusual dearth of comets not of 

 known period, in these parts of the system since the last 

 one was detected by M. Borrelly on December 6, 1874, or 

 more than eighteen months ago. It is true that generally 

 the weather during this interval has been abnormally bad 

 for such work as comet-hunting ; still considering that 

 several of the observers who of late years have given 

 most attention to the search for these bodies, are located 

 in very favoured climates, this appears hardly to explain 

 the absence of any discovery. It may be anticipated 

 that a systematic search for comets in the southern 

 heavens will soon be organised by some zealous amateur 

 in the other hemisphere ; it is certain that he would in 

 this way be likely to render material assistance in the 

 advancement of cometary astronomy, and as we have 

 before urged, he might succeed in bringing to light again 

 one or two comets which were assuredly moving in ellip- 

 tical orbits of short periods when last observed, but from 

 one cause or another have since got adrift, and are not so 

 likely to be recovered in the northern as in the southern 

 hemisphere. 



New Minor Planet.— M. Leverrier's Bulletin Inter- 

 national of July 13 notifies the discovery by M. Paul 

 Henry, at the Observatory of Paris, on the previous 

 evening, of another small planet in R.A. 156. 56m., 

 N.P.D. 111° 59'. This planet, whi^h is estimated I2'5m., 

 is called No. 164, but it is to be remembered that we do 

 not knoiv the actual positions of so many as 164 of these 

 bodies, and until the elements of any newly-detected one 

 are well determined, there is the chance of identity with 

 one or other of several which have been previously 

 observed and even calculated, but for want of continuous 

 observation are now lost. 



A PHYSICAL SCIENCE MUSEUM 



'T^HE President of the Royal Society, Dr. Hooker; 

 -'■ Mr. Spottiswoode ; Dr. Burdon Sanderson ; and Dr. 

 Siemens, had an interview on the 17 th inst. with the 

 Lord President of the Council, the Duke of Richmond 

 and Gordon, and presented the subjoined memorial from 

 gentlemen who have been connected with the Loan Col- 

 lection of Scientific Apparatus at South Kensington. 

 H is Grace discussed the subject of the proposed perma- 

 nent Science Museum with the deputation, and stated that 

 he would consult his colleagues. 



My Lord Duke, 



We, the undersigned, beg to submit for your Grace's 

 consideration the importance of establishing a Museum 

 of Pure and Applied Science ; that is to say, a Museum 

 to contain Scientific Apparatus, Appliances, and Chemi- 

 cal Products, illustrating both the history and the latest 

 developments of Science ; where the methods and re- 

 sults of investigations which have marked important 

 stages in the advancement of Science may be studied, 

 and where also the most highly perfected instruments of 

 the day may be found. 



Among the various advantages which in our opinion 

 would accrue from the establishment of such an Institution, 



