August Z, 1878] 



NATURE 



385 



Minimum Group (nth, 1st, and 2nd Series) ... 

 Intermediate Group (3rd, 4th, gth, and iothSer.es) 

 Ma.ximum Group (5th, 6th, 7th, and 8th Series) 



Of the seventeen cycles of eleven years, between 171 1 and 

 1877, only three have no record of one or more dry years. The 

 great droughts were those of 1722, 1778, 1792, 1825, 184S, and 

 1877, of which four occurred in the minimum group, one com- 

 menced in that group, but culminated in the intermediate group, 

 and one was confined to the latter group. 



Rio de Janeiro, June 12 Orville A. Derby 



The Cell of the Bee 



The following simple construction shows in one figure all the 

 elements of a cell of a honey-comb. On two rectangular axes 

 take OA and OB equal to the side and diagonal of a square. 

 Join A B and bisect it in c. Draw CD normal to A B. Join ad, 

 and complete the rhombus whose sides are ad, db. Then if 

 OA Le a side of the hexagon, adbe is one of the three equal 

 planes forming the trihedral angle which closes the cell. The 

 three short diagonals D e meet in the vertex of the cell, and are 



normal to each other. The three long diagonals ab form an 

 equilateral triangle, o D is the height of the vertex above the 

 hexagonal face of the prism, aed is the angle which the axis 

 of the prism makes with each of the diagonals de. ado is 

 the angle which the axis of the prism makes with each of the 

 edges of the trihedral angle. The diagonals de and AB are 

 in the ratio of the side and diagonal of a square. Such a cell 

 contains a maximum volume with a minimum surface. 



Bardsea Edward Geoghegan 



OUR ASTRONOMICAL COLUMN 



The reported Observation of "Vulcan." — In 

 the telegram received from Mr. Lockyer relating to the 

 solar eclipse which appeared in NATURE last week (p. 353), 

 and which, like many other similar messages, had suf- 

 fered in course of transmission, mention was made of 

 Prof. Watson's observation of an object of 4^ magnitude 

 in R.A. 8h. 26m., and declination 18° o' north, which was 

 neither a known planet nor a star. 6 Cancri, a star of 

 the fifth magnitude, is less than a degree from this 

 position, but the observer would doubtless be aware of 

 its presence. A telegram to the same purport was re- 

 ceived by M. Mouchez, the director of the Observatory 

 at Paris. By the formula deduced by Leverrier from the 

 observations of suspicious objects in transit across the 

 sun' s disc, if the indeterminate k be put = o, the elonga- 

 tion in longitude of his hypothetical body from the sun's 

 centre at the time of totality at Prof. Watson's station 

 would be 5°'9 eastward, and if /l- = — i, 9°'5 westward, 

 neither of which, it will be seen, accords with the position 

 given in the telegram. The fourth-magnitude star, S 

 Cancri, must have been within the limits of the coronal 

 surroundings of the sun, and was only just beyond them 

 during the total eclipse of July 28, 185 1, when no 

 observer, to our knowledge, remarked the star. In the 

 instructions for observing the eclipse issued from the 

 United States Naval Observatory, Washington, and pre- 



pared by Prof. Harkness at the instance of Admiral 

 Rodgers, the superintendent, it is remarked: "As the 

 truth of Leverrier's discovery of an apparently unex- 

 plained motion of the perihelion of Mercury is now 

 established beyond all doubt, it is important to renew the 

 search for an intra-Mercurial planet or planets." And to 

 facilitate the work of such astronomers as might institute 

 a search with considerable telescopic power, a chart was 

 appended to the instructions showing every star so large 

 as the seventh magnitude in that portion of the heavens 

 occupied by the sun at the time. This chart extends 

 from 7h. 32m. to gh. 40m. in right ascension, and from 

 11° to 26^ in declination. 6 Cancri, the only star which 

 appears near the position indicated for Prof. Watson's 

 object, is marked on the chart as a sixth magnitude, 

 which is the estimate of the Uranometria and Durch- 

 mustarimg, but the star has been occasionally rated a 

 fifth magnitude as in the first Radcliffe Catalogue, 

 wherein particular attention was paid to the brightness of 

 the stars. This is only a half-magnitude below Prof. 

 Watson's estimate, but it remains to be seen from further 

 intelligence whether there was any possibility of the star 

 having been the object really noted ; if it were separately 

 remarked, or if the observed position does not admit of 

 such change as would be necessary for identification, 

 then it may truly be said that the American astronomer 

 will have rendered the occasion of this eclipse a memo- 

 rable one in the history of the science. Leverrier's con- 

 fidence in the existence of an unexplained motion in the 

 perihelion of Mercury and the necessity of accounting for 

 it, by admitting the presence cf matter in some form 

 within the orbit of the planet, continued undiminished up 

 to the time of his decease. One of his last communi- 

 cations to the writer of these lines was upon this subject. 



The Lunar Eclipse on August 12. — The eclipse of 

 the moon on August 12 is the only one that will be wholly 

 visible in this country until the year 1884; first contact 

 with the earth's dark shadow at loh. 42m., the middle of 

 the eclipse at I2h. 8m., magnitude 0*59, and last contact 

 at i3h. 34m. On October 4, 1884, there will be a total 

 eclipse of the moon, the middle near 10 p.m., and the 

 passage through the shadow nearly central. 



The August Meteors.— The earth will arrive at the 

 descending node of the orbit of the comet 1862 III., in 

 the track of which the meteors of the August period are 

 found to move, soon after noon on Saturday next ; the 

 comet itself has now receded from the sun to a distance 

 nearly equal to the mean distance of Neptune, to return 

 to these parts of the system probably between 1980 and 

 and 1985. Moonlight interferes this year with observa- 

 tion of the smaller meteors August 9-11, during a part of 

 the night. 



Tempel's Comet. — The following places of this comet 

 are "deduced from M. Schulhof's elements, with the time 

 of perihelion passage, corrected by the early observations 

 at Strasburg by Prof. Winnecke : — 



I. r' AT T' -D-™' t A, „„„„-, North Polar L-g. Distance Intensity 

 i2h. G.M.T. Rigat Ascension. jj.^j^^^^_ from Earth. o£ Light. 



h. m. s. o / 



August 23 ... 16 20 30 ... 109 3 ... 9'90i8 ... o"86 



,, 25 ... — 25 55 ... 109 52 



,, 27 ... — 31 2S ... no 40 ... 9*9079 ... 0*84 



29 ... — 37 12 ... Ill 27 



31 ... — 43 6 ... 112 13 ... 9-9144 ••• 0-82 



September 2 ... — 49 10 ... 112 58 



4 ... 16 55 24 ... 113 42 ... 9-9213 ...-.o-So 



,, 6 ... 17 I 48 ... 114 24 



,, 8 ... — 8 22 ... 115 5 ... 9-9286 ... 077 



,, 10 ... — 15 5 ••• 115 44 



,, 12 ... — 21 58 ... 116 22 ... 9'9365 ... o"74 



,, 14 ... — 29 o ... 116 58 



16 ... 17 36 II ••■ 117 33 ••• 9'944S ... 0-71 



On September 10 the comet pass^3 very near to the 

 orbit of Mars, but the planet is far distant. The dimen- 



