Sept. 26, 1878] 



NATURE 



577 



lopmeut of the Copper-bearing Rocks of Lake Superior, by 

 Raphael Pumpelly; Investigations in Quaternions, by Wash- 

 ington Irving Stringham ; On a New Method for the Separation 

 and Subsequent Treatment of Precipitates in Chemical Analysis, 

 by F. A. Gooch ; On Peirce's Criterion, by Benjamin Peirce ; 

 Note on the Measurement of Short Lengths, by Leonard 

 Waldo ; Contributions to the Botany of North America, by 

 Asa Gray; Spherical Conies, by Gerrit Smith Sykes ; On the 

 Influence of Internal Friction upon the Correction of the Length 

 of the Second's Pendulum for the Flexibility of the Support, by 

 C. S, Peirce; Colour Perception, by G. Stanley Hall; On the 

 Intensity of Terrestrial Magnetism at Cambridge, by Henry 

 Goldmark. Among the foreign honorary members we find the 

 names of J. C. Adams, Airy, Cayley, Sylvester, Clerk- Maxwell, 

 Balfour Stewart, Stokes, Sir Wm. Thomson, Darwin, Joule, 

 W. II. Miller, A, C. Ramsay, Sabini, Bentham, Hooker, 

 Owen, Max Miiller, Rawlinson, Gladstone, Tennyson. 



The receipts of the Giffard Captive Balloon on the first sixty 

 days have been more than 500,000 francs. The sum spent on 

 the construction of the balloon has been realised. It is supposed 

 that the receipts for the month of October will be sufficient to 

 cover the working expenses, so that M. Giffard will be rewarded 

 for his enterprise by the possession of the balloon, machinery, 

 and gas-producing apparatus. 



A MiLtiON tickets have been sold at one franc each for the 

 Paris Exhibition Lottery. Two-thirds of the sum are to be 

 spent in purchasing prizes, the other third being destined to 

 assist the Government in paying the travelling expenses of the 

 working men visiting the Exhibition. 



The additions to the Zoological Society's Gardens during the 

 past week include two Ostriches {Struthio camelus) from Africa, 

 presented by the Hon. H. C. Vivian, H.B.M. Consul- General ; 

 two Secretary Vultures {Serpentarius repiilivorus) from South 

 Africa, presented by C. Rivers Wilson, C.B. ; an Oriental Eagle 

 Owl {Bubo orientalis) from Karenee, Siam, presented by Mr. 

 Charles Fowler ; two Prairie Marmots {Cynomys ludovicianus) 

 from North America, two Smaller Rattlesnakes {Cerotalus 

 milianus) from Canada, presented by Mr. Wilfred G. Marshall ; 

 two Egyptian Gazelles {Gazella dorcas) from Egypt, presented 

 by Mr. Thomas Moss ; three Reddish Finches {Spennophila 

 nigro-aurantia), one Bluish Finch [Spermophila ccsrulescens), one 

 Half -white Finch {Spermophila hypoleuca), one Tropical Seed 

 Finch {Oryzoborus torridus) from South America, presented by 

 Mr. R. C. Batterbee ; three Rufous Tinamous {Rhynchotus 

 riifescens) from Brazil, presented by Mr. J. A. Iliffe ; two Lesser 

 Black-backed Gulls {Larus fuscus), British Isles, presented by 

 Mr. A. H. Cocks, F.Z.S. 



THE FIGURE AND SIZE OF THE EARTH ^ 



H. 



T N addition to the measurement by Picard above-mentioned, 

 ■*■ two other arcs were measured in a north and south direction ; 

 La Hire measured northward towards Dunkirk, and Cassini south- 

 wards towards Perpignan. The result, published by Cassini in the 

 year 17 18, was as follows : — The southern arc gave 57098 toises 

 (Picard's was 57060), and the northern 56960. This result 

 ■was quite opposed to Newton's theory ; it hideed favoured an 

 elongated figure for the earth. There now began among the 

 learned of the time a controversy which was carried on with much 

 bitterness, between the supporters of Newton and Huyghens on 

 the one hand, and of Cassini on the other. Cassini published 

 the results of his measurements in his work, "De la Grandeur 

 et de la Figure de laTerre " (Paris, 1722), and in consequence of 

 the high reputation which he, as Director of the Observatory and 

 member of the Academy, possessed over all France, nearly all the 



' Continued from p. 558. 



French savants took his side. But [the arguments adduced 

 by him were not such as could convince the great number of 

 Newton's followers in all other nations. The French results 

 were all the more objected to, that the measured arcs were 

 much too small to allow one to base thereon a conclusion as to 

 the form of the earth. In order to bring to an end the con- 

 troversy carried on with so much violence on both sides, the 

 French Government sent out in the year 1735 an expedition, 

 consisting|of the astronomers Bouguer,de laCondamine, and Godin, 

 to Peru to measure the length of an equatorial degree. A second 

 expedition, consisting of the academicians Maupertuis, Clairaut, 

 and Lemonnier, was sent to Lapland ; and while the former 

 found the length of a degree at the equator to be 56753 toises, 

 the latter, in connection with Celsius, found the result in latitude 

 66° 20' to be 57437 toises. These results, obtained from the most 

 careful observations and the most accurate calculations, gave the 

 palm to the Newtonian theory, and the amount of flattening as 

 ascertained so nearly agreed with Newton's calculation as to give 

 the greatest confidence in his works. 



It should, however, be mentioned that the Lapland measure- 

 ment was much behind the Peruvian in correctness. Indeed it 

 was soon seen that it was much more inaccurate than Picard's, 

 and therefore the flattening of the earth was based only on 

 Picard's and the Peruvian measurements. But the admirable 

 execution of the Peruvian measurements was of importance also 

 in another respect ; in it, two base-measurements had been made, 

 the southern base being considered a base of verification. This 

 importance, which appeared at a later period, consisted in the 

 fact that the unit of measure used in laying down the base-line, 

 the "Toise of Peru," after it had with the greatest care been 

 brought to Paris uninjured, was instated as the French normal 

 measure, and this standard, at a temperature of 13' R., was 

 appointed as the legal measure of length for France. 



At a later period Freiherr von Zach reduced the length ^ of an 

 equatorial degree to the sea-level and found it to be 56732 

 toises. He made use for this purpose of a second measurement 

 at the equator, carried out by the Spaniards (assisted by Godin)^ 

 between Cuenza and Mira, which embraced a length of 3° 26' 52" 

 and gave 56768 toises as the length of a degree. Since the 

 careful measurement of a degree in Peru — which put a final end 

 to the opposition to the Newtonian theory of the figure of the 

 earth as opposed to the view of Cassini, and proved to all the 

 world as an undoubted fact, that the inhabitants of the earth 

 did not live upon a perfectly spherical planet, but on one flat- 

 tened at the poles; since then has also grown tbe universal 

 desire for accurate knowledge of the dimensions of the earth, 

 as from the amount of its deviation from the spherical form, 

 we expect to form important conclusions as to the origin and 

 development of our planet. Meantime the great progress made 

 in methods of measurement and in instruments, combined with 

 the beautiful results of the constantly-developing mathematical 

 sciences, now promised the best results for new undertakings in 

 reference to measurements of the earth. 



Although the degree measurements carried out up to the 

 middle of last century left no further doubt as to the spheroidal 

 form of the earth, yet, as already said, the Peruvian measurement 

 was the only one that had been carried out with the greatest 

 possible accuracy. But on combining this arc with the French, 

 Lapland, and other known measurements, only differing from it 

 in point of accuracy, results differing much from each other were ob- 

 tained. If we represent the polar and equatorial semi-diameters 



by the letters a and b, the quotient ^ ~ - represents the amount 



of flattening. We thus obtain, by combining the Peruvian and the 

 Lapland measurements, the value ^|-y, the Peruvian and French 

 3^4, and lastly, the French and Lapland xtt- To understand 

 in what way, by means of the data for the length of a degree, and 

 the combining of the data for two or more different parts of the 

 earth's surface, it would lead us to the amount of the flattening, 

 requires considerable knowledge of the higher mathematical 

 methods, and we must not, therefore, enter here on this part of 

 the subject. 



The great differences between the three values referred to, 

 showed how untrustworthy were the measurements hitherto 

 obtained, and this led to endeavours in many quarters to come 

 nearer to the truth by better measurements. Lacaille availed 

 himself in 1750 of his stay at the Cape ot Good Hope to carry 

 out the measurement of a degree, and found for S. lat. 33° 18' 30", 



I This probably refers to the reduction by the Baron de Zach of the 

 observations made in the Peruvian operations. — Mori. Corresp., xxvi., p. 52. 



