456 



NATURE 



\SepL 23, 1875 



refers generally to the discussion of the observations 

 of several of the minor planets with the view to correcting 

 the mass of Jupiter, and to the observations of elon- 

 gations of the fourth satellite by the present Astronomer 

 Royal at Cambridge, which last assigned for the denomi- 

 nator of the fraction 104677. He then remarks upon the 

 circumstance of Bouvard having deduced from his com- 

 parison of the theory of Saturn with seventy-four years' 

 observations a mass so nearly identical with that of the 

 Micanique Cilestej Bouvard left no details of his work 

 behind him ; it is only known that he adopted at the out- 

 set the value of Jupiter's mass admitted at the time, that 

 of Laplace, and M. Leverrier explains that on the method 

 of procedure adopted, Bouvard could not do other- 

 wise than reproduce at the termination of his calcu- 

 lations the value he had assumed at starting. This 

 is illustrated by the result of Leverrier's solution of 

 his own equations of condition, founded upon the 

 much longer period of 120 years, which proved wholly 

 insufficient for the correction of Jupiter's mass. He 

 remarks, with respect to Bouvard's work, that any 

 value of the mass taken arbitrarily within certain limits 

 will allow of a tolerable representation of the observations 

 of Saturn, on the condition that this same arbitrary value 

 is introduced throughout in.the functions representing the 

 mean longitude, mean motion, excentricity and longitude 

 of perihelion ; the elements obtained by Bouvard are 

 therefore found represented by these functions of his 

 arbitrary quantity, and he reverts to the mass assumed at 

 the commencement of his work. 



In conclusion, M. Leverrier insists that the use of the 

 elongations of the fourth satellite for the determination of 

 the mass of the Jovian system, has at present an incon- 

 testable superiority over the employment of the theory of 

 Saturn, on account of the too short period over which the 

 observations as yet extend, but 'in the lapse of time this 

 superiority of the former method will diminish and the 

 use of the perturbations will become the more advan- 

 tageous. It is really, he adds, the same question as that 

 which presents itself with regard to the solar parallax, 

 which is determinable on two methods : the one, geo- 

 metrical, the method by transits of Venus ; the other, 

 mechanical, depending for instance on the large in- 

 equalities in the motion of Mars. The method by transits, 

 so important in 1760, but limited in its means of apphca- 

 tion, must eventually give way to the method of perturba- 

 tions, the accuracy of which will increase unlimitedly 

 with the course of time. 



The first evaluation of the mass of Jupiter is that of 

 Newton in the Cambridge edition of the "Principia" 

 (1713), inferred from Halley's observation of an emersion 

 of Jupiter and his satellite from the moon's limb, giving 

 for the denominator of the fraction (whereby it is usual to 

 express the mass) 1033. In the later editions of the 

 " Principia " the mean distance of the fourth satellite 

 resulting from Pound's observations, to which allusion is 

 made [above, was substituted in the calculation of the 

 mass, which was found to be 1067. (It may here be men- 

 tioned that from later observations by Pound with a 

 micrometer on a telescope of 123 feet focus, on the mean 

 distance of the third satellite, Bessel found for the mass 

 1066). The next attempt in this direction appears to 

 have been made by Triesnecker, Director of the Obser- 

 vatory at Vienna. In 1794 and 1795, making use of a 

 Dollond object-glass micrometer, he obtained a series of 

 measures of distances of all four sateUites, the notice of 

 which appears in the Vienna Ephemeris for 1797. Bessel 

 deduced from them, by a mean of the four values, io55'68. 

 Then follow Bouvard's investigations already mentioned. 

 It is understood that Gauss was the first to bring the per- 

 turbations of the minor planets to bear upon the deter- 

 mination of the mass of Jupiter, and that from the 

 perturbations of Pallas he perceived the necessity of an 

 increase to the mass] adopted by Laplace. The circum- 



stance, so far' as we know, rests upon the authority of 

 Nicolai, who, following in the same steps, discussed 

 observations of Juno at fifteen oppositions, between the 

 year 1804 and 1823, and (in the Berliner Astronomisches 

 Jahrbuchiox 1826) deduced for Jupiter's mass 1053-92. 

 Encke, from fourteen oppositions of Vesta, between 1807 

 and 1825, made its value 1050-36, in a paper published by 

 the Berlin Academy of Sciences in 1826. 



Sir George Airy's observations at the Cambridge 

 Observatory, alluded to by M. Leverrier in his recent 

 notice, are next in order of time. They were commenced 

 in 1832 and continued till 1836. The final result appears 

 in vol. X. of the Memoirs of the Royal Astronomical 

 Society ; it is 1046-77, and depends upon observations on 

 thirty-three nights. Details of the earlier Cambridge 

 observations will be found in vols. vi. and viii. of the same 

 memoirs. Sir George Airy considered it very improbable 

 that there could be an error of a single unit in the deno- 

 minator of the fraction expressing the mass, being led to 

 this opinion by the close agreement of the separate 

 results. 



In the year '1835 Prof. Santini, the present venerable 

 director of the Observatory of Padua, by sixteen nights' 

 measures of the distance of the fourth satellite from both 

 limbs of Jupiter, obtained for the 'mass 1049-2 {Ricerche 

 intorno alia Massa di Ciove, Modena, 1836). 



Bessel's elaborate series of measures of distances of 

 the four satellites commenced in October 1832 and were 

 completed in the middle of 1839. They are fully discussed 

 in his very valuable memoir, BestimniU7ig der Masse des 

 Jupiter, in vol. ii. of his Astronomische Untersuchungen : 

 the definitive value of the mass (p. 64) is 1047-879. 

 Bessel's mass, which has been generally adopted in the 

 calculation of the perturbations of minor planets and 

 comets, and which is so close a confirmation of that 

 deduced by the Astronomer Royal, has receivied much 

 additional support from recent and, as regards method, 

 essentially different investigations. Thus Krueger, of 

 Helsingfors, from the perturbations of Themis, one of the 

 minor planets which approaches nearest to Jupiter, assigns 

 1047-16 ; Axel MoUer, by his masterly researches on the 

 motion of Faye's Comet, 1047-79 '■> while Von Asten, from 

 his last investigations relating to Encke's Comet, finds 

 1047-61. 



THE HOPKINS UNIVERSITY, U.S. 



THE munificent bequests made by wealthy Americans 

 for the promotion of education in the United States 

 frequently excite our astonishment, for they are un- 

 paralleled in Europe at the present time. One of the 

 most unique and well-devised of these bequests has lately 

 occurred. Last year there died a Mr. Jonas Hopkins, a 

 rich citizen of Baltimore, who, after providing for his 

 relatives and leaving various minor benefactions, bestowed 

 the chief part of his estate to found a university with an 

 affiliated medical school and hospital. Both the uni- 

 versity and the hospital receive separate landed and 

 other property of such a substantial character that the 

 value of the total amount is over three millions of 

 dollars. Each institution is to be controlled by a aboard 

 of nine trustees, and the same persons are to be on both 

 boards. The university will have no ecclesiastical or 

 political character or supervision, and will be modelled as 

 far as possible after all that is best in similar American 

 and European institutions. It is intended to give the 

 highest instruction that can be obtained, and the trustees 

 are to act in accordance with the most enlightened ex- 

 perience of the day. The scientific and literary depart- 

 ments will first be organised, and then will follow the de- 

 partments of Medicine and Law, 



No permanent buildings will be erected till all the 

 Faculties are in working order and the wishes of each 

 professor can be carried out ; meanwhile a building has 



