160 



ON THE FOOD OF MAN. 



[1854. 



After the coup d'etat of December 2, 1851, Arago refused 

 to take the oath of allegiance, which was required of hiru in his 

 capacity of director of the Observatory, and thus made manifest 

 once more that politics ought to be kept aloof from Science. 



A life of so much labour had worn down his health. Although 

 attacked with diabetes, he still contemplated putting the last 

 touch to his unfinished works. Bright's malady set in and 

 aggravated his situation, which was complicated with dropsy of 

 the abd imen, attended with effusions, and swelling of the 

 extremities. All announced his approaching end: yet his mind 

 was not for a moment obscured. Shortly before his death, 

 although blind, he superintended in some difficult researches; 

 he asked M. Babinet to prepare for him a table of more accurately 

 determined numbers for the lengths of undulatious, that he might 

 bring to completion a memoir of interferences; and he finished 

 the editing of his Physical researches on the Planets, &c. (fee. 

 He died in the midst of these arduous occupations, on the 2nd 

 of October, at the age of 67^- years, a few minutes after having 

 shaken the hand of M. Biot. 



We have mentioned some of the works which Arago accom- 

 plished in his younger days, These works were completely 

 eclipsed by the discoveries to which his name has since become 

 attached, which embrace the following principles : — 



1. The discovery of chromatic and rotary polarization. 



2. That of Electro-magnets. 



3. That of the magnetism which is developed when bodies 

 are revolved near a magnet. 



Arago was an Encyclopedic genius. Science, Literature, 

 Political and Social economy, his vast intelligence embraced all 

 with equal ability. His powerful faculty of assimilation, popu- 

 larization, and of application of principles, placed him everywhere 

 in the first rank. Whether Orator or Professor, he shone with 

 brilliancy both in political and scientific assemblages. He was 

 distinguished for the perspicuity and elegance of his style, and 

 occupies an eminent place among the prose writers of France. 



In the midst of so much grandeur, Arago led a most modest 

 life. He considered as lazy whoever did not work fourteen 

 hours a day; and such days were for him days of i - e]5ose. 

 Although so absorbed with his occupations, he still found time 

 to appear in the society of Paris as one of its most spirited 

 conversationists. 



While devoted to continued labor, he completely forgot his 

 own interests, and had only what was barely necessary for the 

 support of his family. He left two children, one Emanuel Arago, 

 an eloquent orator of the bar of Paris and of Republican assem- 

 blies, the other Alfred Arago, a distinguished painter. If he 

 has not bequeathed to them a fortune, he has left an immortal 

 name: he has created by his genius a renown more illustrious 

 than all the renown ever gained by arms — which for a long time 

 enjoyed the privilege of giving fame, but now yields the right to 

 the peaceful conquests of science. 



Geology of Gold. 



The geology of gold may now be considered as tolerably well 

 understood. In situ, it is found in the primitive rocks, granite, 

 gneiss, mica slate, clay-slate, and porphyry; and having been 

 freed from its original bed by the decomposition and disintegration 

 of the rocks, and washed out by the rains, it is found in the beds 

 of mountain streams and rivers, and in many alluvial soils in fiat 

 countries, through which mountain torrents occasionally flow. 

 It is most frequently associated with quartz and oxides of iron, 

 and with iron pyrites, sometimes with felspar, hornstone, calca- 



reous spar, barytes, red silver ore, silver glance, sulphuret of 

 copper, peacock copper ore, malachite, the various ores of lead, 

 sulphuret of zinc, grey ore of antimony, cobalt, manganese, copper 

 nickel, arsenical pyrites, orpiment; and this information will en- 

 able parties in possession 'if mineral lands to form a judgment 

 whether specimens from_thcni are worthy of a trial for the produc- 

 tion of the precious metal. In addition to Australia, and the de- 

 velopement of gold in Great Britain and Ireland, it is the opinion 

 of Mr. Calvert, and man) - explorers in Canada, that tLe gold 

 deposits discovered in the valley, and in the sands of the Chau- 

 dierc River, will lead to the dcvclopement of other highly im- 

 portant results in that colony, and we would here remark, that 

 although Mr. Calvert's exertions .ire not duly appreciated in some 

 quarters as they deserve, he undoubtedly is entitled to all credit 

 as the principal pioneer in the present movement 



Central Africa. 



Dr. Vogel in a letter addressed to Colonel Sabine dated 

 Mourzuk, October 14th, 1853, says: — 



"There is no regular rainy season at Mourzuk; but slight 

 showers occur sometimes in the winter and spring; seldom in the 

 autumn. Heavy rain is considered as a great calamit}-, as it de- 

 stroys all the houses, which are built of mud dried in the sun. 

 It also kills the date-trees, by dissolving the salt which exists in 

 large quantities in the soil. About 12 years ago about 12,000 

 date-trees perished in the neighbourhood of Mourzuk, on account 

 of rain which continued for seven days. The prevailing winds 

 are south and east; the strongest generally west or north- west. 

 I have seen whirlwinds two or three times pass through the 

 town, — a phenomenon which was common in the desert between 

 Bencolua and Mourzuk: all the whirlwinds which I observed 

 turned from the east to north, and went to south 



" In December and during the first half of January, the 

 thermometer falls at sunrise, at Mourzuk, as low as 42°, and 

 in places exposed to the wind water freezes during the night. 

 At Sakna, I could not find any one who could remember having 

 seen snow. At Tripoli we had heavy dews at night, and I ob- 

 served the same until we had passed a small chain of mountains 

 fifteen miles north of Sakna. Thence we had no dew, and it 

 was often impossible to obtain the dew point with Daniell's 

 hygrometer. In the desert the thermometer generally rose till 

 4 p. m., from the sand (which was sometimes heated to 140°,) 

 giving out its heat. Earthquakes are sometimes felt. Great 

 numbers of shooting stars were observed on the 7th, 8th, and 

 31st of July ; very few on the evenings of the 9 th, 10th, and 11th 

 of August; but they were again very numerous on the 1st, 2nd, 

 and 3rd of October." 



On tlie Food of Man.* 



BY DK. LYON TLATF-UK, C E., F. K. S. 



The author commenced by adverting to our very imperfect 

 acquaintance with the statistics of Food. We are still ignorant 

 regarding the quantity of the different proximate constituents of 

 aliment necessary for man's sustenance, even in his healthy and 

 normal condition. If the epiestion were asked — How much 

 carbon should an adult man consume daily? — there would be 

 scarcely more than one reliable answer, viz., that the soldiers of 

 the body-guard of the Duke of Darmstadt eat about 11 oz.f 

 of carbon in the daily supply of food. 



*This is an Abstract of a Lecture given at the Weekly ETening Meeting at the 

 Royal Institution, Friday, May 6, 1S53. 



-jXiebig states it at a higher amount, but this is a re-calculation from the new food 

 table. 



