12 REPORT— 1872. 



continue to hold a high position among civilized nations, the most anxious care 

 must be given to the establishment by the state of such an organized system for 

 the advancement of science and the utilization of the work of scientific men as wiU 

 be in harmony with similar organizations in neighbouring states — for examples, 

 France, Germany, and Russia. 



Appkndix. 



Certain conclusions at which Professor ZciUner arrives in the investigation of 

 several points bearing on the theory which he defends are, quite independent of 

 the latter, of high scientific value. 



First, with reference to the density of atmospheric air, which (in accordance 

 with the considerations mentioned in stating his views) he supposes to fill the 

 interstellar space everywhere, he assumes for the purposes of calculation that the 

 temperature of space is that of melting ice, and finds that the lower limit of 



density for a portion of gas in space is -ttwjj- of that of the air at the earth's surface, 



a value so small that if a mass of air which, at its ordinary density upon the 

 earth's surface, occupies a volume of one cubic decimetre (a litre) were reduced 

 to the density expressed by this fraction, it would fill a sphere whose radius would 

 not be traversed by a ray of light in less than 10"'* years. These values indicate a 

 density which would have no appreciable effect whatever upon rays of light or 

 upon the motion of bodies in space, and which would become still less if the tem- 

 perature of space be taken, with Fourier, at — 60° C, or with Pouillet, at — 1.32° C. 

 But as every solid body must, by virtue of its gravitative energy, condense the gas 

 into an atmospheric envelope round itself, the density of the latter will solely 

 depend on the size and mass of the body. Professor Zollner finds by calculation 

 that, for instance, the density of air thus forming an atmosphere round the moon 



must be frisai of that of the air of the earth's surface. This is in accord with the 



fact that no trace of a lunar atmosphere has as yet been detected. But the 

 values become very great for the larger planets, quite great enough to manifest 

 absorptive effects upon the light reflected from them. Considering that there are 

 peculiarities in the spectra of Uranus, Neptune, and also of Jupiter, which appear 

 to indicate atmospheric influences. Professor Ziillner's results are not without 

 deep interest, and certainly suggestive of further inquiry. 



Secondly, with reference to the supposition that a body may be at the same 

 time under the influence of gravitative and electrical agencies, it was necessary for 

 the author of this theory to discuss the quantitative ditt'erence in their effect upon 

 ponderable masses at a distance. The discussion shows that, if the mass increases, 

 gravitation preponderates over electricity ; if the mass decreases sufliciently, the 

 contrary takes place. It follows that the cometary nuclei, as masses, are subject 

 to gravitation, while the attenuated vapours developed from them yield to the 

 action of free electricity of the sun. Professor Zollner has based upon Hankel's 

 numerous and careful researches on the determination of atmospheric electricity, 

 in absolute measure, an analytical inquiry into the motion of a small sphere under 

 the action of gravity and atmospheric electricity, which leads to some remarkable 

 results. Supposing the free electricity of the sun to be not greater than that 

 repeatedly observed on the earth's surface, and to be uniformly distributed, it 

 would communicate to a sphere having a diameter of 11 millimetres and a weight 

 of yi^ of a milligramme, and starting from the sun, by the time it had moved as far 

 away as the mean distance of Mercury, a velocity per second of 3,027,000 metres, 

 or 408'4 German geographical miles *. This velocity is such that in two days it 

 would pass over a space of 70,.540,000 German geographical miles, a magnitude 

 quite of the same order as those recorded by cometary astronomy. The discussion 

 was undertaken to prove that there is no need for assuming the existence of anj' 

 unknown repulsive agency, but that electrical energy not greater than that observed 

 on the earth's surface is amply sufficient to account satisfactorily for the pheno- 

 mena presented by cometic trains. 



* Fifteen to a degree of longitude on the Equator. 



