64 



NATURE 



[May 17, 1900 



therapeutics, both from the theoretical and practical sides, and 

 it will show practitioners what can be accomplished by hypnotic 

 suggestion. 



Although a large amount of work has been published upon 

 the physical properties of dilute solutions of single electrolytes, 

 the experimental study of solutions of mixed electrolytes, notwith- 

 standing its great interest from the point of view of the electrolytic 

 theory of dissociation, has not been worked at so extensively. The 

 theoretical discussion of such mixtures leads to a set of ecjuations 

 somewhat difificult to solve ; but since Prof. MacGregor, of the 

 Dalhousie College, Halifax, Nova Scotia, showed how to solve 

 these equations by a simple graphical method, systematic re- 

 searches have been carried on at this college on the properties of 

 such mixed solutions of electrolytes. A recent paper, by Mr. J. 

 Barnes, in the Transactions of the Nova Scotian Institute of 

 Science, deals with the depression of the freezing point in salts 

 containing a common ion ; and the results show that in the case 

 of mixtures of potassium chloride and sodium chloride, and of 

 sodium chloride and hydrochloric acid, and of all three, it is 

 possible, with the ionisation coefficients obtained by Prof. Mac- 

 Gregor's method, and on <;the assumption that the molecular 

 depression of an electrolyte in a mixture is the same as it would 

 be in a simple solution of the same total concentration, to predict 

 the depression of the freezing point within the limits of the error 

 involved in observation and calculation. 



The additions to the Zoological Society's Gardens during the 

 past week include a B jnnet Monkey ( Macacus sinicus, 6 ) from 

 India, presented by Lady Malcolm, of Poltalloch ; a White- 

 crested Tiger Bittern {Tigrisoma leucolophum) from West 

 Africa, presented by Mr. W. F. Marshal ; four Chaplin Crows 

 (.Corvus capellanns) from Southern Persia, presented by Mr. 

 B. T. Ffinch ; a Cinereous Vulture ( Vultur monachus), 

 European, presented by Mr. W. E. Found ; a Common Boa 

 {Boa constrictor) from South America, presented by Mr. F. H. 

 Preston; two Egyptian Foxes {Cams niloticus) from North 

 Africa, two Prevost's Squirrels {Sciurus prevosti) from Malacca, 

 a Ring-tailed Coati {Nastia rufd) from South America, two 

 Porto Rico Pigeons {Columba squamosa) from the West Indies, 

 a Sclater's Cassowary {Casuariiis sclateri), two Red-sided 

 Eclectus {Eclectus pectoralis) from New Guinea, four Logger- 

 head Turtles {Thassochelys caretta) from Tropical seas, twelve 

 Elegant Terrapins {Chryseinys scripta elegans), seventeen 

 Lesueur's Terrapins {Malacoclemmys lesueuri) from North 

 America, twelve Adorned Terrapins [Chrysemys ornala) from 

 Central America, seven Reeves's Terrapins {Dainonia reevesi) 

 from China, deposited ; five Hairy Armadillos {Dasypus villosus) 

 from La Plata, four Common Indian Starlings (Sturnus mem- 

 bieri), a Bengal Fox {Cams bengalensis) from India, two 

 Meyer's Parrots {Poeocephalus meyeri) from South-east Africa, 



four Australian Sheldrakes {Tadorna tadornoides), five 



Wood Swallows {Artamus sordidus) from Australia, six 

 Sulphury Tyrants {Pitangus sulphuratus), a Black-pointed 

 Teguexin (Ttipinambis nigropunctatus) from South America, 

 purchased ; a Crowned Lemur {Lemur coronaltis), six Common 

 Wolves (Cams lupus), a Llama {Lama peruana) born in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN 



Unpublished Observations at Radcliffe Observa- 

 tory, 1774-1838. — In a pamphlet containing a reprint of an 

 article in Monthly Notices, vol. Ix. pp. 265-293, Dr. A. A. Ram- 

 baut, Radcliffe observer at Oxford, calls attention to a very 

 valuable collection of astronomical observations which are pre- 



NO. 1594, VOL. 



62] 



served at the Radcliffe Observatory, but have not been reduced 

 or published. Two of the Oxford astronomers, Profs. Hornsby 

 and Robertson, spent a large amount of labour in reducing 

 Bradley's observations made at Greenwich from 1710-1762, and 

 further continued his work by themselves maintaining a system- 

 atic and regular series of observations for sixty-five years, from 

 1774-1838. These were all made with the instruments sup- 

 plied by Bird to the Radclift'e Observatory at its installation, 

 consisting of two quadrants each of 8-feet radius, a transit in- 

 strument of 8-feet focal length, and a zenith sector of 12-feet 

 focus. The observations have all been methodically copied in 

 a similar form to their printed edition of Bradley's observations, 

 and contain altogether about 130,000 transits and 60,000 zenith 

 distances. Dr. Rambaut states that his staff at present could 

 not undertake the reductions ; but, in order to show the extreme 

 importance of the data available, he has made a selection 

 of them, giving the probable errors compared with other 

 observers. 



The planets and sun have received considerable attention, 

 there being about 8000 observations of the sun alone, a number 

 little less than that on which Leverrier's tables were founded, 

 and, moreover, covering the period when the corrections to the 

 mean longitude of the sun, as deduced at Greenwich, Paris and 

 Konigsberg, are most discordant. 



The working list of stars includes about 4870 of those ob- 

 served by Flamsteed and Bradley, so that direct comparisons 

 could be made in the reductions. Their great value would be 

 specially apparent in the question of proper motions, filling up 

 as they do the long gaps between Bradley and Piazzi, or Bradley 

 and Pond. Specimens of Dr. Rambaut's reductions are given 

 in the paper to show the high degree of accuracy attained by 

 the observations. 



Maximum Duration for a Total Solar Eclipse. — 

 Mr. C. T. Whitmell, president of the Leeds Astronomical 

 Society, recently read a paper showing the results of calcula- 

 tions he had made in the endeavour to ascertain what is the 

 maximum duration possible for a total solar eclipse {Monthly 

 Notices, R.A.S., vol. Ix. pp. 435-441). After considering the 

 several effects of the varying distances of sun and moon from 

 the earth in determining size of umbra and velocity of shadow, 

 he cites the following five conditions as required for maximum 

 duration of totality : — 



(i) The new moon, at or very near a node, must also be at 

 the most favourable perigee possible ; (2) the sun must be at 

 apogee ; (3) during totality, which should be observed at local 

 noon, the moon's shadow should run along a parallel of latitude, 

 in order that the diurnal movement of the observer may be for 

 the time parallel to the motion of the moon, thereby producing 

 its full effect in detaining him within the umbra ; (4) the sun 

 and moon should be in the zenith, so that the umbra may be 

 as large as possible ; (5) the observer should be on the equator, 

 so that his linear velocity may be as great as possible. 



Of these, owing to the sun and moon 7tot moving in the plane 

 of the celestial equator, it is impossible that ^4) and ( = ) can be 

 simultaneously fulfilled ; (5) is more favourable than (4). 



Taking the moon' 



horizontal parallax as 61' 22", 

 earth's radius as 3963 miles, 

 moon's ,, io8i'5miles. 



and using the present accepted eclipse values of the diameters 

 of the sun and moon, the maximum totality will occur near the 

 middle of July, at noon, in geocentric north latitude about 4" 52', 

 and will last about 7m. 40s., the sun being at apogee with a 

 parallax of 8"'70. This is on the assumption that the declinations 

 of the two bodies are considered practically constant during 

 totality. The author gives the following list of long duration 

 eclipses, calculated by Mr. Crommelin from Oppolzer's data : — 



Position of noon point 



1 901 May 18 

 1919 May 29 

 1937 June 8 

 1955 June 20 

 1973 June 30 

 1991 July II 



noon 

 h. m. 



6 41-6 



7 5-9 

 7 199 

 7 24-5 

 7 196 

 7 107 



Longitude Latitude 



97 E. 



18 W. 



131 W. 



117 E. 



6E. 



105 W. 



2 8. 



4N. 

 10 N. 

 15 N. 

 19 N. 



22 N. 



