3o8 



NATURE 



[Feb. i8, 1S75 



Mohl's statement, that the pollen of Mimulns mosc/intus and 

 Miiimliis lutcus takes several lorms, before writing his letter. I 

 may inform him that tlic figure — in the " One Thousand Objects" 

 — to which he alludes was not copied from the " Micrographical 

 Dictionary," as he states. Had Mr. Smith first taken the pains 

 to read what so excellent an authority as Dr. Hugo Mohl 

 has written on pollen, and seen his figures, perhaps his remarks 

 would have taken a different form. He may have observed but 

 one form or one aspect of the pollen grains of Mimulns differing 

 from the figures criticised, yet botanists will hesitate to accept 

 his interpretation in opposition to so excellent a physiologist as 

 Dr. H. Mohl, on the faith of his ad cajitandiim observations. 



M. C. Cooke 



OUR ASTRONOMICAL COLUMN 



Variable Stars. — Amongst the stars which deserve 

 attention on account of probable variability, the following 

 may be mentioned ; we take them in order of right 

 ascension. 



1. X Eridani, first suspected by the late Capt. Gilliss, 

 of the U.S. Naval Observatory, Washington. It has 

 been variously estimated between mag.|4 (Lalande, Arge- 

 lander, Heis) and 6 (Gilliss, Santini). 



2. 33 Herculis. The variation of this star hardly admits 

 of doubt. It is called 6 mag. by Ilamsteed, Bradley, 

 Piazzi (who observed it nine times), Taylor, and Robinson, 

 and is so entered on Wolfers' Chart ; Lalande calls it 7, 

 and this is the magnitude assigned in the Radcliffe 

 observations 1867-68. Bessel and Argelander (in the 

 " Durchmusterung") considered it only 8; Gilliss also 

 drew attention to this star. 



3. Lalande 31384. In the " Histoire Celeste," p. 291, 

 this star is called i>\. Sir John Herschel, in his third 

 series of observations with a 20-ft. reflecting telescope, 

 estimated it 5, and remarked that it is not in Piazzi. 

 Bessel and jSantini, who has four observations, call it 7 ; 

 it is 5 '5 in the " Durchmusterung," and 6 on Bremicker's 

 Chart. 



4. 41 i Aquilae looks suspicious ; D'Agelet has four 

 observations, 6, 4'5, 6, 6 ; Lalande two, 3|, 4 ; it is 5 in 

 Piazzi, 4"2 in " Durchmusterung." 



5. Piazzi XXI. 21. D'Agelet, who observed this star 

 twice, calls it 8 on one occasion, and g'lo on the other. 

 It is 8 in Piazzi, 6 and 6i in Lalande, 9 in Bessel, and 7'S 

 in Argelander (Durch.) 



6. 17 t Andromeda. This star has been variously esti- 

 mated between 3^4 and 7. Flamsteed says 4, Bradley 7, 

 D'Agelet 3^4 in 1783, and 6 in 1784 ; Lalande twice calls 

 it 5, and once 4 ; Piazzi, who has ten observations, 7 ; it 

 is 4 in the Atlases of Argelander and Heis, and 3'9 in 

 the first RadclitTe catalogue. Bradley and Piazzi com- 

 pared with the Oxford catalogue, in which much atten- 

 tion was given to magnitudes, appear to certify the 

 variability of light. 



Piazzi I. 4, 16 Leonis Min., and 32 Vulpccuhe, one of 

 Gilliss's suspected stars, also deserve attention, and 

 observations of x (Bayer) Cygni are especially desirable, 

 great perturbations having been exhibited in the times of 

 maxima of late years, which, with others previously indi- 

 cated, it has not yet been found possible to represent 

 satisfactorily by any formula. The variable is the true 

 X Cygni, Flamsteed having affixed this letter to his 

 No. 17 in this constellation ; the cause of it is now under- 

 stood, |Bayer's x iiaving been faint at the dates of Flam- 

 steed's observations. The var. has (i875'o) R.A. igh. 

 4Sm. 46s., N.P.D. 57° 24'. 



Prof. Schonfeld, in his new catalogue, enters the Rev. 

 T. W. Webb's variable in Orion, as S Orionis, and places 

 it (for 1855) in R.A. 5h. 21m. 51s., and N.P.D. 94° 4S'7. 

 As a first rough approximation to elements, he fixes a 

 minimum to the beginning of December 1872, and assigns 

 a period of from thirteen to thirteen-and-a-half months, 

 the limits of variation 8-3 to less than 12-3. 



Occultation"of Antares, 1819, April 13. — We refer 

 to this occultation on account of an interesting observation 

 made by Burg at Vienna. He records the emersion on 

 the dark limb of the moon at I2h. 3m. 22s. or 23s. 

 apparent time, but remarks that at I2h. 3m. I7S'I he 

 noted the emergence of a star of from sixth to seventh 

 magnitude, which after nearly five seconds suddenly 

 appeared as a star of the first magnitude ; and, writing to 

 Bode, he suggests that Antares might be a double star, 

 with the companion so close to the principal star, that 

 good telescopes had not shown it. Bode's explanation 

 was not a happy one. In a note he remarks ; " Antares 

 is no double star," and he goes on to attribute the phe- 

 nomenon witnessed by Burg to the intervention of a lunar 

 atmosphere. The Vienna observation, however, proves that 

 the small star was then separated from the large one by a 

 measurable quantity. It may be remembered that at the 

 emersion of Antares in the occultation of 1856, March 26, 

 which was observed by the late Rev. W. R. Dawes) at 

 Wateringbury, and Mr. Whitbread, F.R.S., at Cardington, 

 both observers noted the interval between the appearance 

 of the small blue star and its bright neighbour as seven 

 seconds ; the difference of colour was very marked on this 

 occasion ; Burg does not refer to it. Occultations of 

 Antares are coming on again, but no one of them is visible 

 in this country up to the end of the year 1878. 



Encke's Comet. — From M. Stdphan's observations at 

 Marseilles on January 27 and 29, published in M. Lever- 

 ritr's Bullftui International ai the ilthinst., it appears 

 that Dr. von Asten's ephemeris gives the comet's place 

 with great precision ; indeed, the error on the 29th (the 

 best observation) was less than fifteen seconds of arc. 

 M. Sti^phan remarks : — " La comite offre I'apparence 

 d'une petite tache laiteuse, \ peine perceptible, produisant 

 sur la r<5tine plutot des pulsations intermittentes qu'une 

 sensation continue." We are able to add, that on the 

 31st ult. it was the extrcnium visibile with a 7-inch 

 refractor. The following positions are for 8 P.M. Green- 

 wich time ; — 



R.A. N.r.D. 



distance 



o , from the Earth. 



81 5-3 I-8l8 



So 41-0 1798 



80 i6-i 1776 



79 507 I 754 



79 247 1730 



78 58-2 1705 



78 31-1 1-678 



Feb. 21 o 10 25 



,. 23 o 14 33 



,, 25 o iS 49 



>. 27 o 23 13 

 March i o 27 45 



,,3 o 32 26 



,.5 o 37 16 

 Winnecke's Comet. — Prof. Oppolzer considered that 

 the error of his predicted time of perihelion passage in 

 the present year would^ probably not exceed two hours. 

 We find, on comparing the Marseilles observation on the 

 morning of the 2nd inst. with his elements, that the error 

 is likely to be within this limit, or about o'>o764, the pre- 

 dicted time too late. With this correction the error in 

 geocentric longitude disappears, and that in latitude is 

 very trifling. 



MR. HAMILTON'S STRING ORGAN 

 T N the Philosophical Magazine for February there is 

 -•- a paper by Mr. R. Bosanquet on the mathematical 

 theory of this instrument, in which, however, as it ap- 

 pears to me, the principal points of interest are not 

 touched upon. As the remarks that I have to offer will 

 not require any analysis for their elucidation, I venture 

 to send them to Nature as more likely than in the Plii- 

 losophiral Magazine to meet the eyes of those interested. 

 The origin of the instrument has led, as I cannot but 

 think, to considerable misconception as to its real acous- 

 tical character. The object of Mr. Hamilton and his 

 predecessors was to combine the musical qualities of a 

 string with the sustained sound of the organ and har- 

 monium. This they sought to effect by the attachment of 



