46 



NATURE 



\Nov. 1 6, 1871 



have not the same properties. Gelatine, unHke osseine, 

 does not exist in organism, but is produced by chemical 

 transformation resulting from the action of water and heat 

 upon the bony tissue ; gelatine, moreover, is completely 

 soluble in water, while osseine is not so. For these reasons 

 the two substances would doubtless be different in their 

 alimentary capacities, and deductions drawn from the 

 influence of one upon the human system ought not in any 

 way to prejudice the other. Of course, says M. Fremy, 

 osseine cannot be expected to fulfil the same duty as a 

 complete aliment ; such, for instance, as bread, or meat, 

 but must be employed in conjunction with some other 

 suitable material. In the same way gluten, which is 

 simply flour freed from starch, oil, and soluble substances, 

 would alone be powerless to support life and health. If 

 regarded in the same light as fibrine, casein, and albumen, 

 and associated with other bodies, osseine would be found 

 a valuable aliment. White meat, calf's head, neatsfoot, 

 &c., contain much bony tissue, and their nutritious quahties 

 are incontestable. 



Of this osseine, then, bones are said to contain 35 per 

 cent., the mode of separation being simply to slice the 

 bone very thinly, and to treat the same with dilute hydro- 

 chloric acid ; hard white bones, free from fat, are most 

 suitable, and some care and attention in manipulation is 

 of course necessary, so that the product may be perfectly 

 sweet and free from any taint or unpleasant odour. For 

 if disgust is once aroused against this kind of food, as 

 indeed against any other for that matter, no amount of 

 pushing or puffing can force it into the public market. 

 Should, therefore, any trace of acid be perceptible after 

 preparation of the osseine, it is recommended that the 

 product be treated with an alkali of some kind, for 

 example, lime or carbonate of soda, but this must obviously 

 be done with due care and discretion. The cost of this 

 aliment is about one franc per pound, whereas gelatine of 

 good quality costs from four to five francs. 



As regards the best method of cooking or curing, IVI. 

 Fremy recommends the swelling of the mass with hot 

 water, and then boiling for about an hour, when the tissue 

 becomes soft and phable ; it may be seasoned in the 

 cooking, or may be allowed to cool and then kept for 

 thirty-six hours in brine. If eaten warm with admixture 

 of some fat and vegetables the osseine is decidedly 

 palatable. Owing to its large constituent of nitrogen it is 

 extremely nutritious, and, furthermore, forms a comestible 

 not liable to become putrid. 



It is right to mention that on some of the points 

 enumerated by M. Fremy, exception is taken by M. Dumas 

 and others, who are not so confident of the real value of 

 osseine as an alimentary substance, those gentlemen 

 maintaining the injurious nature of gelatine ; M. Chevreul, 

 however, confirms to some extent M. Fremy, and states 

 that osseine is decidedly more nutritious than gelatine. 



Other measures for improving the alimentation of Paris 

 were taken during the siege, but these for the most part 

 present little novelty. Mr. Wilson's plan for salting 

 the carcases intact, and thus preserving the meat in an 

 almost fresh condition, was resorted to, that gentleman 

 bringing his personal staff from Ireland to afford as- 

 sistance just at the instant of closing the gates of the 

 metropolis. The assistance of M. Georges, whose plan 

 of preserving meat is both original and peculiar, was like- 

 wise obtained ; this invention, which has been practised 

 it is saidwith much success in America, is adapted more 

 particularly for the curing of mutton rather than beef, and 

 consists in treating the meat in a bath acidified with hy- 

 drochloric acid, and afterwards in a solution of sulphite 

 of soda. In this condition, after further sprinkling with 

 sulphite of soda, the flesh is packed in tins and soldered 

 down ; the sulphite of soda acting upon the hydrochloric 

 acid gives rise to sea salt and sulphurous acid, thus* en- 

 suring the perfect preservation of the meat. 



H.B. P. 



THE TEMPERATURE PRODUCED BY SOLAR 

 RADIATION 



SIR ISAAC NEWTON determined the intensity of 

 solar radiation by observing the increment of tem- 

 perature of dry earth on being exposed to the sun. In the 

 latitude of London at midsummer, dry earth acquires a 

 temperature of 150^ in the sun at noon and 85° in the 

 shade, difference about 65° Fah. This difference Sir Isaac 

 Newton regarded as a true index of the intensity of solar 

 radiation ; hence his celebrated demonstration proving 

 that the comet of i5So was subjected to a tempera- 

 ture 7,000 times higher than that of boiling water 

 (212° X 7,000 = 1,484,000° Fah.).* The comet when in its 

 perihelion being within one-third part of the radius of the 

 sun from his surface, we have to add the diminution of 

 temperature, o'44, attending the dispersion of the rays in 

 passing through the solar atmosphere and the remainder of 

 the stated distance from the sun. Accordingly, the demon- 

 stration showing that the comet of 1680 was subjected to a 

 temperature 7,000 times higher than that of boiling water, 

 establishes a solar temperature exceeding 2,640,000^ ; and 

 if we add o'2i for the retardation of the rays in tra- 

 versing the terrestrial atmosphere, it will be found that 

 the temperature deduced from the experiments with in- 

 candescent radiators, and our actinometer observations, 

 differs scarcely \ from that roughly estimated by the 

 author of the " Principia." In order to comprehend fully 

 the merits of the method of determining solar intensity 

 conceived by his master mind, let us imagine an extended 

 surface of dry earth, one half of which is shaded, the 

 other half being exposed to the sun. Dry earth being a 

 powerful absorbent and radiator, and at the same time a 

 bad conductor, the central portion of the supposed surface 

 evidently cannot suffer any loss of heat by lateral radia- 

 tion ; while the non-conducting property of the material 

 prevents loss by conduction laterally or downwards. Con- 

 sequently, no reduction of temperature can take place 

 excepting by radiation in the direction of the source of 

 the heat. Removing the shade, during an investigation, 

 it will be found that, notwithstanding the uninterrupted 

 radiation of the exposed substance upwards, the intensity 

 will gradually increase until an additional temperature of 

 about 65 " Fah. has been acquired. Indisputably, this 

 increase of temperature is due to unaided solar radiation. 

 Evidently the accidental interference of currents of air 

 need not be considered. Besides, if the dry earth is con- 

 fined within a vacuum, such interference may be entirely 

 obviated. It is scarcely necessary to point out that the 

 generally-adopted mode of measuring the sun's radiant 

 heat by thermometers, is in direct opposition to the prin- 

 ciple involved in the method under consideration. The 

 meteorologist, in place of preventing the bulb from radiating 

 in all directions and guarding against loss of heat by 

 convection, puts his thermometer on the grass, or suspends 

 it on a post, one half of the convex area of the bulb re- 

 ceiving the sun's radiant heat, while the other half is per- 

 mitted to radiate freely, the whole being exposed to the 

 radiation from surrounding objects and to the refrigerating 

 influence of accidental currents of air, in addition to the 

 permanent current produced by the ascending heated 

 column above the bulb. This explains the cause of the 

 perplexing discrepancies in meteorological records. The 

 extent of the diminution of intensity of solar radiation 

 occasioned Ijy cold air acting on the bulb, and by the 

 latter radiating freely in all directions, is demonstrated in 

 the most conclusive manner by the result of observations 

 made with the instrument described by Pfere Secchi in 



* Sir Isaac Newton lias been criticised for comparing the temperature to 

 that of red-hot iron, " a term of comparison indeed of a very vagne de- 

 scription," it is said in " Outlines of Astronomy." This ciiticism is far from 

 being correct, since the demonstration clearly shows what is meant by the 

 term red-hot, viz. a temperature 3"5 times that of boiling water. The 

 reference to red-heat, exceeded "two thousand times," was evidently in- 

 tended to furnish some adequate notion of the inconceivably high degree of 

 temperature involved in the computation. 



