288 Queries and Answei'S. 



taken from a small slab of limestone which I obtained 

 from Dudley. It ai)pears to be the caudal termination 

 of a species of trilobite, differing materially from the 

 A'saphus caudatus in being furnished with a number 'of 

 rounded processes and very minute transverse lines down 

 the middle lobe. There are two of these specimens 

 upon this slab, rather smaller than the drawing, mixed 

 with fragments of the Calymene variolaris, A. cau- 

 datus, various testacea, and madrepores ; but no head 

 or upper portions can be traced, which might lead to 

 an idea of its complete figure. 1 shall be glad to be 

 informed if this specimen has been before noticed. 

 Yours, &c. — F. /. Feb. 5. 1831. 

 The Atmosphere never dark on a ivindy Night. — Several years since, 

 when travelling by night in the mail coach, in the depth of winter and 

 during the absence of the moon, I was surprised to observe, that, though 

 dense clouds covered every part of the horizon, and not a single star could 

 be seen, yet the night was far from being dark, and large objects near the 

 road were easily discerned. On expressing my surprise to the driver, he 

 replied, '* The wind is very high, and during a great many years that I have 

 been upon the road, I never knew it to be dark on a windy night." The 

 observation was at that time new to me ; but subsequent experience 

 has convinced me that it was true. Many plausible explanations might 

 be offered ; but I congeive the most rational one would be, to attribute 

 it to the evolution of a small quantity of light from the whole atmo- 

 sphere by the pressure of the particles of air during a high wind. When 

 atmospheric air is suddenly and violently compressed in a tube, suf- 

 ficient heat is evolved to ignite combustible substances, and I believe 

 a sensible quantity of light is also given out at the same time ; it is, there^ 

 fore, not unphilosophical to infer that a lower degree of pressure, on an 

 immense mass of air, may evolve a portion of light from each particle, 

 which may collectively afford a low degree of illumination, sufficient to 

 render large objects perceptible in the night. Perhaps some of your corre- 

 spondents can give you a better explanation of the cause of this phe- 

 nomenon. 



Being for many years an amateur star-gazer, I have invariably observed 

 that, however clear the sky might be, if the stars appeared to swim in the 

 focus of an excellent achromatic object glass, and the more delicate double 

 stars could not be defined, the following day was always more or less 

 rainy. 



In the course of the last summer, when the weather for a few days 

 seemed to promise a fine settled state of the atmosphere, I observed about 

 midnight what appeared to be a strong twilight in the north-west, but too 

 luminous to be produced by the refraction of solar light. After observing 

 it for some time, a single ray only rose towards the north, and disappeared. 

 This was sufficient to prove the phenomenon to be the common aurosa 

 boreahs. The light continued steady for a very long time. The following 

 day the weather changed to rainy, and continued so for many days. The 

 aurora was too near the horizon to be observed in London, It bore a 

 strong resemblance to common twilight. 



In December, or the latter end of November, 1821, there was one of 

 the most tremendous thunder storms at Geneva I ever remember to have 

 witnessed : it occurred about four o'clock in the morning. The evening 

 previous the mercury in the barometer fell suddenly lower than it had 

 been observed in that city for forty years. The storm was followed by a 

 general change in the state of the weather,'which had been previously fine 

 and mild. — B. Hampstead, Nov. IS30. 



