288 



NATURE 



[Feb. lo, 1876 



observers in connection with the work in question, and 

 the measures now published not only confirm this favour- 

 able opinion of the instrument, but bear inherent testi- 

 mony to the care and patience expended on the observa- 

 tions, and will doubtless be received as an important and 

 valuable contribution to double-star astronomy, and 

 especially by those who are occupied with similar obser- 

 vations, or the investigation of the orbits of the binary 

 systems. Amongst the more interesting of the revolving 

 stars, the Catalogue has measures of 77 Cassiope?e, 36 

 Andromedas, a Geminorum, (, Cancri, w Leonis (which 

 difficult object was just divided at the end of March 1873), 

 ^ Ursas Maj»ris, y Virginis, ^ Bootis, rj Coronae, 2 1938, 

 C Hercuhs, 70 Ophiuchi, 2 3062, &c. The interesting, 

 though difficult binary 2518 (Eridani), is probably within 

 the power of such an instrument, but does not appear in 

 the Catalogue ; it may be suggested that it is not too late 

 to examine this object in the present season, the actual 

 angle may probably be found very considerably in advance 

 of that obtained by Prof. Winnecke in 1864, and a first 

 approximation to the form of the orbit may soon be 

 practicable. 



Jupiter's Satellites. — If we take a mean of the 

 measures of the diameters of the satellites by Struve at 

 Dorpat, and by Engelmann at Leipsic, we shall have for 

 apparent diameters at the mean distance of the pri- 

 mary : — 



I. ... i"-o48 II. ...o"-9ii ••• III. i"-5i3 ... IV. i"-278 

 and with a solar parallax of 8"*875, the true diameters in 

 English miles will be : — 



I. ..; 2,435 ••• n. ... 2,115 ••• in. 3,515 ... IV. 2,970 

 The angular diameters at the centre of Jupiter, are : — 

 I. ... 3i''4 II. ... i/i III. ... i/-8 IV. ... 8'-6 



and the mean distances from the centre of Jupiter : — 



1 266,700 miles 



n 424,300 „ 



III 676,800 „ 



IV 1,190,400 „ 



The diameter of the planet's equator is assumed to be 

 88,200 miles, as lately given in this column. 



THE DRAINAGE OF THE ZUYDER ZEE. 



THE Dutch are a people who in many respects com- 

 mand the respect of the world. Their little country 

 possesses comparatively few natural resources, and yet 

 they have made so much of it, and they have been com- 

 pelled to cultivate the virtues of frugality and industry to 

 such an extent, that the people as a whole are probably 

 better off than those of any other country in the world. 

 Small as the country is, it is only by the exercise of great 

 skill and constant watchfulness that they are able to pre- 

 vent its being overwhelmed by the German Ocean. In this 

 unfortunately they have not always been successful. Over 

 and over again has the sea burst in upon them, laying waste 

 their dearly-loved country, and sweeping away thousands 

 of the inhabitants. It has only been after many severe 

 lessons that they have learned how to keep the invader 

 back. And within recent years they themselves have 

 taken the offensive, and determined to drive out old Nep- 

 tune from lands which he has possessed for centuries. 

 Even in the seventeenth and eighteenth centuries they 

 succeeded in draining many small areas of land, and 

 during the present century many marshes and lakes have 

 been brought under cultivation, including Lake Haarlem, 

 upwards of 40,000 acres in extent. In this way about 350 

 square miles of land, mostly devoted to pasture, have been 

 reclaimed, and that entirely by means of windmills. 



Now, however, that the applications of steam-power 

 have reached such perfection, this enterprising people have 

 determined upon an enterprise much more gigantic than 



any they have hitherto attempted, — nothing less than the 

 drainage of the Zuyder Zee. Until the end of the thir- 

 teenth century the area now occupied by that arm of the 

 ocean seems to have been mostly dry land, with a lake in 

 the centre, which by means of a river drained into the 

 German Ocean. At the time mentioned, however, in 

 1282 according to some authorities, the sea broke through 

 what is now the Strait of Helder, and converted the dry 

 land into a gulf. 



For many years the drainage of the Zuyder Zee has 

 occupied the attention of the Dutch Government and of 

 engineers, but it is only since the improvements in the 

 application of steam that the idea has been seriously en- 

 tertained. At last a scheme has been adopted, after 

 many years' careful research and consideration, for the 

 details of which we are indebted to the French journal 

 EExplorateur. 



As early as 1865 a Dutch Credit Foncier Association 

 took up the scheme at the suggestion of Mr. Rochussen, 

 an eminent statesman, and employed two engineers, M. 

 Beijerinck, who drained the Haarlem Lake, and M. 

 Stieltjes. These reported on the practicability of draining 

 the southern, the shallowest and most fertile, half of the 

 inland sea. Soundings were made, and numerous speci- 

 mens of the bottom brought up, and in short a thorough 

 investigation made from a geological and agronomic 

 point of view. The result of these investigations was 

 most favourable, and the specimens submitted to the 

 analysis of a distinguished agricultural chemist, M. van 

 Bemmelen, having been found to consist of alluvial clay 

 or loam of the first quality and of great depth, over 

 an extent of four-fifths of the bottom of the sea, the So- 

 ciety entered into negotiations with the Government. A 

 Government Commission was appointed to consider the 

 whole question from an economic and scientific point of 

 view, and after an investigation lasting about two years, 

 gave in their report in April, 1868. This report was in 

 favour of granting a concession to the Credit Foncier, 

 whenever that company could present a definite plan that 

 would obviate all existmg objections. The Society, after 

 further consideration, requested the Government to dele- 

 gate a commission of specialists to report further on the 

 scheme, taking into consideration all the interests con- 

 cerned, and to decide upon the plan best adapted to carry 

 the scheme into execution. After three years thorough 

 consideration the Commission gave in a voluminous report 

 in April 1873, which declared that the project from an 

 engineering point of view was practicable ; that the 

 clearing of the new lands would be a difficult and very 

 expensive enterprise, but that the experience acquired and 

 the progress of science would furnish the means of over- 

 coming these difficulties, and of making the enterprise a 

 benefit to the country. 



The drainage will be effected in that part of the gulf 

 lying between the provinces of Guelderland, Utrecht, and 

 North Holland, over an extent of 195,300 hectares (about 

 740 square miles, nearly equal to the area of Surrey, and 

 about 100 miles larger than the Dutch province of Zee- 

 land), by means of a principal dike or embankment, of 40 

 kilometres in length, 50 metres broad at the base, and 

 raised 5 metres above the ordinary tides, to be con- 

 structed from the left bank of the mouth of the Yssel to 

 the island of Urk, and from hence to the town of Enk- 

 huyzen in the province of North Holland. The inclosed 

 area will be divided into squares, and numerous pumping 

 steam-engines will then be set to work, having a collective 

 force of 9,400-horse power. The Commission estimates 

 that the work will be entirely accompHshed in sixteen 

 years, and that it will cost a sum of 10,000,000/. not includ- 

 ing the interest of the capital employed ; or 1,600,000/. for 

 preparatory works, provisional circular canals, &c., about 

 2,760,000/. for the construction of the dike, and the rest for 

 the purchase of engines, the drainage proper, and the con- 

 struction of reservoirs, internal canals, roads, railway 



