Jan. 28, 1875] 



NATURE 



251 



having revised and discussed anew the observations of 

 the Sun, made since the time of Bradley at Greenwich, at 

 Paris, at Kcinigsberg, to the number of 9,000, we have 

 been forced to quite a different conclusion, viz., that the 

 observations of the Sun are far from what they ought to 

 be, on account of the systematic errors which affect 

 them, and that there is no discordance between theory 

 and observation which may not be attributed to errors in 

 the latter. 



In spite of all, the discussion of the observations of the 

 Sun led us hence to an important result connected with 

 the great question which agitates, at this moment, the 

 scientific world ; a result which surprised ourselves, so 

 much had the determination of the parallax of the Sun, 

 deduced by the director of the Berlin Observatory from 

 the Transits of A'enus in 1761 and 1769, inspired a false 

 confidence. I arrived at the conclusion that the paralla.x 

 of the Sun, estimated then at S'57", ought to be increased 

 by the 25th part of its value. 



Soon after, the comparison of the theory of Venus 

 with the observations led to the same result, the necessity 

 of increasing by }.■- the parallax of the Sun. 



Finally, the theory of Mars led, in its turn, to a con- 

 clusion not less precise. It was proved that we could not 

 account for the cnssmble of the observations of Mars 

 without increasing the movement of the perihelion by 

 about one-eighth. This was the reproduction of the 

 same fact as in the case of Mercury, and the conclusion 

 to be drawn from it vi^as the same, viz., that the planet 

 Mars must be subject to the action of a quantity of matter 

 till tlien neglected, and that it must be estimated at the 

 eighth part of the mass of the Earth. 



But then two hypotheses were possible, as we explained 

 at the seance of June 3, 1861 : either that the matter till 

 then left out of the count resided in the belt of the small 

 planets as a whole, or that it must be added to the Earth 

 itself. In the latter case, and as a consequence, the 

 parallax of the Sun must be increased by the 24th part of 

 its received value, that is to say, that we would be led to 

 the same result already deduced from the theories of the 

 Sun and of Venus. 



Meantime M. Fizeau has given a method for deter- 

 mining the speed of light, by a physical experiment, on 

 the surface of the earth ; and from this measurement, 

 combined with the quantity of the aberration of the stars, 

 we Icnow that we can deduce the parallax of the Sun. 



Foucault, on his part, had devised a plan of solving 

 the same question by another method, and he was 

 engaged in realising the experiment. I pressed him 

 strongly to carry it into execution. We know that in the 

 seance of Sept. 22, 1862, Foucault announced that he had 

 fixed the rate of light at 298,000 kilometres per second ; 

 hence, by adopting the quantity of aberration determined 

 by Struve, 8'S6" resulted for the parallax of the Sun, a 

 number corresponding to an increase of i-30th of the 

 received value. 



M. Cornu, in the important paper read by him at the 

 last sitting, resolved definitively the question by the em- 

 ployment of the method of M. Fizeau. He was good 

 enough to refer to the determination which I presented to 

 the Academy at the sitting of July 22, 1872, based on the 

 celebrated and very exact observation of the occultation 

 of the star ■^- Aquarii by the planet Mars, an occultation 

 observed in 1672 by the three great astronomers. Richer, 

 Picard, and Rcemer. 



Moreover, we shall combine materials obtained from 

 various points of view on this delicate question, and will 

 further increase by discussion the great interest which 

 will be presented by the materials collected with so much 

 devotion by the various expeditions destined to the obser- 

 vation of the present Transit of Venus. For this reason, 

 and because the method which results from the occultation 

 of t//'' Aquarii is present under a form precise and striking, 

 we shall shortly ask permission from the Academy to 



deposit the work in its hands, after having given it the 

 necessary developments. 



Jupiter and Saturn have given rise to a theoretic work 

 the extent of which has been considerable, on account of 

 the very great mutual perturbations of the two planets. 

 The comparison of the theory of Jupiter with the obser- 

 vations has presented, after the proper modifications of 

 the elements, a complete harmony. The tables of Jupiter 

 have also been adopted by the editor of the Nautical 

 Almanac to serve for the preparation of that important 

 work. I owe to our confrere Mr. Hind, superintendent 

 of the Nautical Almanac, the satisfaction of thus seeing 

 adopted by the astronomical world the various tables of 

 Mercury, the Sun, Venus, Mars, and Jupiter, so far as 

 they have appeared. 



The tables of Saturn are now constructed, and their 

 comparison with the observations is almost finished. 



The theories of Uranus and of Neptune being also 

 completed, it only remains further to eftect their compari- 

 son with the observations. 



The profound knowledge which my excellent colleague 

 M. Gaillot, chief of the Bureau des Calculs, and rfiember 

 of the Council of the Observatory, has of these matters, 

 and the devotion with which he has assured the laborious 

 construction and comparison of the tables of Jupiter 

 and Saturn, are to me a sure guarantee that the final 

 work will be, whatever happens, carried out to the end. 



RUSSIAN FORESTS 



VEGETATION in the fossil or recent state forms the 

 main source of the wealth and prosperity of most 

 nations, either directly or indirectly : directly, in the case 

 of the vast subterranean deposits of the remains of 

 former plant-life in Britain, as also in the broad expanses 

 of land covered with timber-trees in Russia. According 

 to recent statistics * the extent of the forests of Russia in 

 Europe is about 442,897,500 acres, or forty per cent, of 

 the whole area. The forests are vei-y unequally dis- 

 tributed, and internal communication is still very im- 

 perfect in many parts of the empire ; hence much of this 

 wealth is at present unavailable. Every year, however, 

 the facilities for transport are increased, and there is a 

 corresponding augmentation in the amount realised. 

 Nearly sixty-five per cent, of the forest land is situate in 

 the four governments of the North — Archangel, \''ologda, 

 Olonetz, and Perm ; this equals sixty-five acres to each 

 inhabitant. The governments of the South arc relatively 

 poor in timber, and in some parts almost treeless ; but 

 since 1842 the forest administration has been engaged in 

 remedying this defect by planting largely. Between 1S66 

 and 1S70 upwards of 20,000 acres were planted, exclusive 

 of the action of private owners. The principal trees are 

 the Scotch pine, spruce fir, larch, birch, lime, aspen, and 

 oak. To these may be added for the governments of the 

 South, though relatively playing an unimportant part in 

 commerce, the elm, ash, beech, hornbeam, maple, various 

 poplars and willows, &c. The value of the forest products 

 exported in 1871 amounted to 16,026,553 roubles, of 

 which more than one-third came to this country. But 

 the internal consumption gives a better idea of the im- 

 mense wealth of these forests. It is only possible to give 

 an approximate estimate of the value, which Mr. Werekha 

 states must be at the very least 265,450,000 roubles per 

 annum. In Russia, wood is still either the only or the 

 principal fuel used. The railways consume wood for 

 fuel to the annual value of 7,200,000 roubles. Wooden 

 drinking-vessels, platters and spoons, take the place of 

 pottery and metal in many districts, except in the houses 

 of the rich. Mr. Werekha estimates that forty million 

 wooden spoons are made every year ; but Mr. \Vesch- 

 niakoft', in his account of the domestic industries of 

 Russia, puts the figure at thirty millions. 

 * " Notice svir ks Forets et leurs Produits," etc. Par P. N. Werekh.i. 



