METEOROLOGY. 441 



of Die clouds, and travelled during more than an hour out of tlie view 

 of the land, the aeronauts were unable to perceive the aureole round 

 the shade of the balloon, which remained visible during the whole of the 

 excursion on the upper face of the clouds. I explain this circumstance 

 by the fact that the cloud was formed by solid water and that the aure- 

 ole was less brilliant, the same relation between these two phenomena 

 existing for luminosity as between halos and rainbows. The aeronauts, 

 having remained at an altitude of two to three hundred meters from the 

 clouds, were unable to perceive the colored rings which were visible 

 to me and M. Brissonet, navigating only at a few meters above similar 

 legions of icy particles. It may have also occurred that our friends 

 were blinded by the light from the sun, which at four o'clock was very 

 powerful, and so detrimental to their eyes that before entering the 

 clouds they were unable to look fixedly at the earth to ascertain their 

 path. It is the first time I have heard of aeronauts having experienced 

 the want of colored spectacles to inspect our jilanet. {Nature, xxvi, 

 p. 89.) 



The effect of haze upon the telescopic definition of stars has been ob- 

 served by G.W. Royston-Pigott. He gives several illustrations of the 

 extreme steadiness and perfect definition of astronomical objects ex- 

 amined through slight haze, very especially the haze due to the London 

 fog. He suggests that the effect of haze is apparently to diminish 

 the intensity of refraction, but the explanation commonly received is, 

 we believe, that the haze acts by way of equalizing the distribution of 

 heat, thus diminishing the currents of hot and cold air, to which the 

 phenomena of scintillation are largely due. {Nature, xxv, p. 77.) 



J. J. M. Perry communicates some data on the fitness of the climate 

 of Alnwick, in Northumberland, for astronomical observations. The 

 summary for one year (1881) is as follows (the review is rather an 

 instructive one, as showing the great amount of work accomplished by 

 English astronomers in spite of the climatic obstacles) : 



Two hundred and twenty-nine nights were completely overcast ; 51 

 were partially so (but of these 4 were too cloudy for observations) ; and 

 85 were clear. Thus, 132 nights ought to have been available for ob- 

 servations. Of these the definition on 51 was very bad, on 9 bad, on 

 14 fair, and on 2 very fine. Wind prevented observations on 16 nights, 

 frost and snow combined on 15, on 2 frost alone, and on 1 snow alone. 

 On 161 was absent from home, and on 3 engaged. Total, 132. {Nature, 

 xxv, p. 317.) 



XII. — a Periodicity and suNsroxs. 



An anonymous writer in Nature gives a table of mean departures of 

 the monthly temperatures from their normal values for a hundred years 

 in England. He concludes that those winters which give a mean tem- 

 perature 3^ in excess were immediately followed by summers warmei 

 than usual. {Nature, xxvi, p. 35.) 



