Juiy 19, 1877] 



NA TURE 



235 



The period of revolution is 2434"2 days, or 6' 664 years, 

 therefore nearly identical with that of Biela's comet up to 

 1852. The comet passed its perihelion on May 10. It 

 will net arrive at its least distance from the earth until 

 October 20, but the theoretical intensity of light diminishes 

 from the present time, indeed has been on the decrease 

 since the middle of May ; the comet may be a test object 

 on the borders of the constellations Eridanus and Orion 

 in September and October. 



It is probable that this comet had been revolving in its 

 present restricted orbit for many years previous to its 

 discoveiy in June, 1S51. It certainly does not furnish a 

 parallel case to that of Brorsen's comet, which was de- 

 tected at its first perihelion passage after the attraction of 

 the planet Jupiter had impressed upon it the actual form 

 of orbit in May 1842. The nearest approach of D'Arrest's 

 comet to Jupiter during the revolution immediately pre- 

 ceding discovery, took place at the end of September 

 1849, when the distance was ri36. 



The Binary Star a Centai'ri. — Mr. Ellery com- 

 municates to the Royal Astronomical .Society recent 

 measures of this, the finest and most interesting of all 

 the revolving double-stars. Taking means the following 

 epochs result from the Melbourne measures : — 



187672 Position 51 •! Distance 4'3 

 1877-25 ,, 69-1 „ 3-13 



Mr. IMaxwell Hall (Nature, vol. xv. p. 510) supplies the 

 following : — 



:877'I4 Position 64°'4 Distance 3"'3 

 Mr. Ellery state.s that the distance in 1S62 was 10", but 

 this must be an over-estimate with the meridian in- 

 strument ; a mean of seventy micromefrical measures by 

 Mr. Eyre B. Powell at Madras, gives for iS62'2, a 

 distance of only 6"79, a result no doubt entitled to great 

 confidence. The first minimum of distance appears to 

 have occurred in 1S56. Capt. Jacob's measures for i856'27 

 giving 3"'89, and a maximum of about 10' followed in 

 1868-70. It is to be hoped that the star will now be 

 frequently measured micrometrically with all possible 

 precision, though the brilliancy and closeness of the 

 components may render such measures difficult. A 

 practised computer should be able to throw some li^ht on 

 the real nature of the orbit from the data already in our 

 possession, but the continued regular measurement of the 

 star at this critical period cannot fail to be of great 

 importance in extending our know^ledge of the motion 

 in this system. The reliable estimate of its distance 

 resulting from the observations of Henderson, Maclear, 

 and Moesta, vastly increases the interest attaching to it. 



GEOLOGICAL NOTES 

 Geological Survey of the United Kingdom. — 

 The gradual progress of the English and Scottish 

 Geological Surveys has brought the members of the two 

 corps almost within sight ot each other. The line of 

 demarcation between the two kingdoms being nearer the 

 base of operations from Scotland, has been sooner 

 reached from that side. From Berwick-on-Tweed south- 

 westwards the work has been carried up from the north 

 to the English border through the range of the Cheviot 

 Hills, and down the valley of Liddesdale to the Solway. 

 To prevent any subsequent risk of the lines from either 

 side not fitting accurately, the officers on the Scottish 

 border are at present engaged in running their boundaries 

 into Cumberland and Northumberland for such a short 

 distance as may be required to leave them in a position 

 where they can be easily taken up by the advanced guard 

 of the English Survey. When this and some few isolated 

 areas are completed, the whole of the south of Scotland 

 between the Tay and Clyde and the English border will 

 have been geologically surveyed, and the Scottish staff 

 will then be engaged on both sides of the flanks of the 



Highlands. Already ground has been broken, and some 

 progress has been made on the north side of the Grampian 

 chain. On the English side the mountainous lake district 

 is all surveyed, while the work is so well advanced in 

 Cumberland that it may probably be completed up to the 

 Scottish border by the end of this year. Considerable 

 pi ogress has likewise recently been made on the eastern 

 side in pushing the survey northwards in Northumber- 

 land, though a considerable tract of that country still 

 remains unmapped towards the Cheviots and Tweed. 

 Among the south-eastern counties the survey is advancing 

 through Norfolk, Suffolk, and Cambridgeshire, v/hile in 

 the south-west some of the maps which were made in the 

 early days of the Geological Survey are being re-surveyed 

 and brought up to date in West Somerset and Devon. 



Geological Survey of Canada. — The Report of 

 this Survey for 1S75-76 has just arrived. In size, general 

 interest, and geological value, it fully equals its well- 

 known predecessors, while in regard to maps, sections, 

 and other illustrations, it even surpasses them. Briefly told, 

 its story is this — The Philadelphia Exhibition absorbed 

 much of the time and thought which would otherwise 

 have been expended on the field-work, laboratory, and 

 museum duties of the officers. But the director need not 

 regret this temporary suspension of the usual operations 

 of his staff, for there can be no doubt that the display of 

 rocks, minerals, and fossils, made by Canada at the 

 Centennial Exhibition, so universally admired brought 

 the mineral resources of the dominion and the skill of 

 its geological survey before the world with such promi- 

 nence as could hardly have been attained even with the 

 ablest maps and memoirs. Mr. Selwyn's own labours 

 from April to November, 1S75, embraced an exploration of 

 parts of British Columbia where likewise Mr. George M. 

 Dawson, who has lately been appointed to the Canadian 

 Survey, has been actively employed. Prof. Macour, 

 besides his geological work, made a careful botanical 

 survey of the region traversed, and his detailed narrative 

 appears in this Report. Mr. Ellis was sent into the North- 

 west Territory to make a series of borings. Mr. Bell 

 explored the country between James Bay and Lakes 

 Superior and Huron ; while in the eastern parts of the 

 Dominion detailed surveys were made in the coal-fields 

 of Nova Scotia, in New Brunswick, and in Cape Breton. 

 Besides these explorations others were continued by Mr. 

 Wnnor in Ontario. Of these Mr. Selwyn remarks that 

 they prove the existence in Western Quebec and Eastern 

 Ontario of a massive red orthoclase gneiss without visible 

 stratification, lying probably unconformably under the 

 vast crystalline masses containing Eo^ooii. He suggests 

 that what is called Lower Laurentian may have to be 

 termed Middle, the fundamental red gneiss becoming the 

 Lower. 



Excrementitious Deposits in the Rocky Moun- 

 tains. — A recent paper to the Philadelphia Academy by 

 Mr. Henshaw, on the excrementitious deposits in the 

 Rocky Mountain region, sustains Prof. Cope's view that 

 they were made by big-eared rats, a species of Keotoina, 

 probably A^. cincrea. They consist of vegetable matter, 

 sometimes with a bitumen-like look, and varying from this 

 appearance to that of pill-like excrements. In a crevice of 

 the rocks one deposit had a depth of two feet, and con- 

 tained also some small twigs and " birds' " feathers. " The 

 mass was evidently the accumulation of years, and had 

 served as a nest. Throughout was a large amount of 

 hard droppings from which the urine had passed, and 

 whose nature was unmistakable. The urine, charged with 

 a certain amount of excrementitious matters, had filtered 

 through to form the singular deposits." Water or the 

 urine has carried the portions it could dissolve down the 

 faces of walls, and deposited it on shelves where no ani- 

 mals without wings could reach,and sometimes on the roofs 

 of cavities. All the regions where these deposits occur are 

 inhabited by the AV()/ri;;/(7, which is essentially a vegetarian 



