1853] 



MEETING OF THE BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



07 



classified under three general heads: — I. Older observations recorded 

 of Luminous Meteors. II. Continuation of Catalogue of Luminous 

 Meteors from the Report of 1851-2. III. An Appendix, containing 

 letters and drawings, giving a more detailed account of some more 

 Remarkable Meteors. The number of meteors tabulated under the 

 second head "was very large. The records were preserved under the 

 following heads: — 1. Date; 2. Hour and minute when seen; 3. Ap- 

 pearance or magnitude; 4. Brightness and Colour; 5 Train, or sparks; 

 H. Velocity, or duration; 7. Direction, or altitude; 8. General Remarks; 

 ;). Place; II) Observer; II Reference. This report gave rise to a very 

 animated and long sustained conversation. 



Mr. Grove explained the frhree opinions advanced as to the possible 

 origin of these interesting objects. Atone time it had been maintained 

 that they were bodies projected upon the earth from the moon; next, 

 it had been supposed that they had a chemical oirgin in our own at- 

 mosphere; — and lastly, it was held that they were probably planetary 

 bodies whose orbits t aversiug that of the earth when they met it a 

 node, the planetary mass falling into our atmosphere ignited aud put 

 on one of the varied ph. ses of a meteor. Mr Grove stated, that the 

 first opinion was now universally abandoned; — that the second though 

 still claiming supporters, was not considered the most probable; — aud 

 that the third opinion was all but universally row received among sci- 

 entific men a- the most probable account of their origin. He fortified 

 each of these statements, giving k the leading reasons which led to the 

 rejection or adoptio nof each. 



'On the Composition and Figuring of the Spccnla for Reflecting Tcles- 

 eope'x,' by Mr. boLLirr — The writer commenced by staling that he 

 had given his attention to this subject for years, and that he was more 

 than ever .convinced of its importance by the decided conclusion to 

 which facts had led him that reflectors, when once well aud carefully 

 made, were far less apt to deteriorate than refractors. In order to be 

 intelligible to the Section, it was necessary for him to go over some 

 ground familiar to the public since the researches of Lord Rosse, Mr. 

 Las-ell aud Mr. Nasmith. He stated that, he considered it to be amatter 

 of prime importance that the copper aud tin should be used inexact 

 atomic proportions He, following the numbers giveu by Berzelius, 

 used the following proportions — copper, 32; tin, 1 74. Lord Rosse's 

 are, copper, 32; tin, 14 9. As the metal when thus composed was very 

 hard, brittle, and difficult to work, he found that he could render it ca- 

 pable of reflecting white light equally well, if not better; and at the 

 same time of taking a very uniform aud beautiful polish, by introduc- 

 ing a little nickel in place of the tin, — and the following proportions 

 he found on trial best: — copper 32; tin, 15 5; nickel, 2. He also found 

 the introduction of a very small quantity of arsenic, useful in preventing 

 the oxidation of the tin when melting. Silver, as used by Mr. Lassell, 

 he also found excellent; but he was against the use of fluxes, as most 

 injurious. The author passed over the casting aud grinding with very 

 slight notice: but dwelt on the composition aud figuring of the polisher 

 as of great importance. The composition as used by him was pitch 

 resin, aud a small admixture of flour was found useful. The surface 

 he grooved with concentric equidistant circular grooves, — aud not in 

 parallel aud cross grooves, as used by Lord Rosse and Mr. Lassel. — 

 These concentric grooves he crossed by radial grooves, widening as 

 they receded from the centre, so as to be bounded by curved outlines. 

 By giving proper form and dimensions to these curves the parabolic 

 form could be most accurately giveu to the speculum in the process of 

 polishing. 'I lie form of the curved outlines of these radial grooves he 

 found should be parabolic. Ke concluded by stating the importance of 

 not haviug the speculum too thiu, aud of using proper precautions 

 in mounting aud supporting it, t > avoid any chance of the form being 

 altered. 



Dr. Scoresby regretted that having been in another Section he had 

 not heard the early part of the communication of Mr. Sollitt; but he 

 rather thought Lord Rosse used concentric grooves ii: his polisher as 

 well as parallel aud cross grooves. Prof. Stevelly confirmed the accu- 

 racy of this statement: aud added that his memory was quite clear 

 that Lord Rosse. considered it very important to use the copper and 

 tin iu atomic proportio s, aud said iu his papers on it that uniformity 

 of composition could not otherwise be hoped for. He' also recognized 

 the importance of using thick specula; the last which he had cast 

 beiug nut less than five iuches thick He also had used aud recom- 

 mended resin to be used to harden the pitch and flour for a purpose 

 by which experience he had leari.t to be important. Lord Rosse had 

 also by the several motions and adjustments which he had connived 

 for the speculum aud the polisher reduced the figuring of the speculum 

 to an almost certain function of time; so that after the speculum had 

 been a certain number of hours under the action of the polisher, he 

 was well assured that the proper figure had been attained. Professor 

 Stevelly briefly described these motions and adjustments; and stated 



that the actual result was, an enormous circular disc of six-feet aper- 

 ture, without crack or flaw, and of a splendid uniform polish, and re- 

 flecting light from objects of a perfectly natural tint. 



' On the Surface Temperature, and Great Currents of the Koiih Atlantic 

 and Northern Ocean,' by the Rev. Dk. Scokesby. — 'I he author com- 

 menced by pointing out the great importance to Physical Geogra- 

 phy of the subjects he proposed to discuss, particularly as they teuded 

 in the economy of Nature, to furnish a compensating instrumentality 

 against the extremes of condition to which the fervid action of the ver- 

 tical sun in the tropical regions, and its inferior aud more oblique 

 action iu the polar regions, were calculated to reduce the surface of 

 the earth. Our knowledge of all the currents of the ocean, with per- 

 haps, one exception; the Gulf-stream, which had beeu, in its more 

 important features, carefully examined and surveyed, and more espe- 

 cially in the Amirican Coast Suivey, — was derived from the compari- 

 son by navigators of the actual positiou of the ship as determined 

 from time to time with its position as calculated from what sailors 

 technically called the " dead reckoning," or the course steered, aud 

 the distance run as determined by the log, an instrument by no means 

 perfect. The determination, however, of oceanic currents, to which the 

 present communication referred, depends simply on induction from 

 observation of temperature, on that mainly of the surface. Such ob- 

 servations, indeed, only become available under considerable differ- 

 ences betwixt the mean atmospheric and oceanic temperatures; and 

 where they may seem to indicate the region from which peculiar 

 qualities of the sea are derived, they cau afford little, if any, informa- 

 tion as to the precise direction or strength of the current, so indicated, 

 yet still the geueral results are found important and useful. 'J he re- 

 searches of the author embrace those in the Greenlaud Sea, the North, 

 Sea, and a considerable belt across the North Atlantic. To those in 

 the North Atlantic he wished at present to direct attention; aud to a 

 belt of it embraced within the limits of a series of passages chiefly by 

 sailing vessels between England, or some European port, and New 

 York. Of these passages, sixteen in number, four were performed by 

 the author himself; and twelve supplied by an American navigator, 

 Captain J. C. Delano, an accurate scientific observer. The observa- 

 tions on surface temperature discussed amount to 1153, gathered flora 

 a total number of about 1400. Usually Captain Delano recorded six 

 observations each -day during the vox age, atinteivals of four hours. 

 Seven of the passages were made in the spring of the year, — two in... 

 the summer, — oue in autumn, — and three in winter. Taking the mid 

 die day of each passage the mean day at sea was found to be May- 

 18th or 19th, — a day fortunately coiucideut in singular nearness with 

 the probable time of the mean annual oceanic temperature. '1 he au- 

 thor had laid down the tracks of the ship iu each of the voyages on a 

 chart of M creator's projection, and the principal observations on Sur- 

 face Temperature were marked in their respective places. The ibscr- 

 vations were then tabulated for meridians of 2° iu breadth, from Cape 

 Clear, longitude 10° W-, to the eastern point of Long Island, longitude 

 72°W.,— embracing a belt of the average breadth of 2-0 miles ou a 

 stretch of about 2,(i(0 miles across the Atlantic. The results -n ere the 

 following: — 1. Highest Surface Temperature northward of latitude 

 40°, 7j°; lowest 32°; range 39°— Mean Surface Temperature, as de- 

 rived from the means of each meridioual section 56°, whilst the mean 

 atmospheric, temperature for the corresponding period was 51°-2 — 3. 

 Range of Surface Temperature within each meridional section of ,2°, 

 8 1 ., at toe lowest, being in longitude 20-22° W., aud at the greatest 

 36 s , being within the meridian of t2 l'4°\v".— 4- Dp to longitude 4C° 

 the Surface Temperature never descended below 50°;— the average 

 lowest of the sixteen meredional sections being 51°'88, aud the avc- 

 jage range being 11°'3. 5. hi the succeeding fifteen sections, where 

 the lowest temperature was 32°, the average lowest was 37°\1, and 

 the average rauge 29°-7. This remarkable difference iu the Tempera- 

 ture of the eastern and western halves of the Atlantic passage, the au- 

 thor said was conclusively indicative of great ocean currents yielding 

 a mean depression of the lowest meridional temperature from 51°'&8 

 to 37°-l, or 14°-8 and producing a mean range of the extreme of tem- 

 perature on the western side of almost thrice the amount of the ex- 

 tremes on the eastern side,— or, more strictly, in the proportion of 

 29°.7 to 1 1° 3. The author drew attention to a diagram which he had 

 laid down along the entire belt curves showing the whole range of the 

 lowest depressions of temperature aud highest elevation, with the 

 means at each longitude distinsuished by different shading, aud 

 pointed out how the inspection of this as well as of the tabulated re • 

 suits afforded striking indication of the two great cuneuts, one des- 

 cending fr..m the Polar, the other ascending from the Tropical regions, 

 with their characteristic changes of cold aud heat. Iu classifying the 

 results, the author considered the entire belt of the Atlantic track of 

 the passages as divided into six divisions of 10° of longitude eich, 

 aud these into meridional stripes of £° each, omitting the two first 

 degrees next the European end, or about 8 J mi'es westward i f Ir« land 



