NATURAL PHILOSOPHY. 151 



was never quite free from water. From ascents made bcfoi-e and 

 after sunset, Mr. Glai.sher concludes that the laws which hold 

 good by day do not hold good by night ; indeed, it seemed prob- 

 able that at night, for some little distance, the temperature may 

 increase with elevation instead of decreasing. From experiments 

 made on solar radiation with a blackened bulb thermometer, and 

 with Herschel's actinometer, it was inferred that the heat-rays 

 from the sun pass through space without loss, and become effect- 

 ive in proportion to the density or the amount of water present in 

 the atmosphere through which they pass. If this be so, the pro- 

 portion of heat received at Mercury, Venus, Jupiter, and Saturn, 

 may be the same as that received at the earth, if the constituents 

 of their atmospheres be the same as that of the earth, and greater 

 if the amount of aqueous vapor be gi-eater ; so that the effective 

 solar heat at Jupiter and Saturn may be greater than at either the 

 inferior planets. Mercury or Venus, notwithstanding their far 

 greater distances from the snn. This conclusion is most impor- 

 tant, as corroborating Professor Tyndall's experiments on aqueous 

 vapor. Experiments on the wind showed that the velocity of the 

 air at the earth's surface was very much less than at a high eleva- 

 tion. A comparison of the temperature of the dew point, as 

 shown by different instruments, gave results proving that the tem- 

 perature of the dew point, as found by the use of the dry and wet 

 bulb thermometers, and Daniell's hygrometer, is worthy of full 

 confidence as far as the experiments went. — Reader. 



THE EFFECT OF SUNSHINE ON FIRE. 



At the meeting of the Scientific Association at Buffalo, Prof. 

 Horsford, of Cambridge, read a very interesting paper on the above 

 subject. 



He commenced by alluding to the popular notion that sunshine 

 deadens fires ; mentioning that the fii-es in grates, in rooms havino" 

 southern exposures, burn briskly in the early part of the day, 

 slacken before noon, and revive again before sunset. Stoves and 

 ranges, that bake well in the autumn, winter, and spring, fulfil 

 their oiRce but indifferently in the height of summer. Some fur- 

 naces, in which iron is generally smelted without difficulty, can- 

 not, in very hot terms, be brought to a working heat. While the 

 popular mind asci'ibes these effects to some agency of the sun, 

 scientific men are disposed to regard the effects as rather apjjarent 

 thaa real. 



The first recorded research bearing upon the subject was made 

 as long ago as 1825, by Dr. Thomas McKeever, who found, as he 

 conceived, the popular impression sustained. In his experiments, 

 a given weight of wax taper was consumed quicker in the dark 

 than when exposed to the sun. A given length of candle required 

 less time for combustion in the dark than in sunshine. A given 

 weiglit burned quicker in a painted lantern than in an uncoated 

 lantern, both alike exposed to the sun. 



These experiments did not find acceptance with Gmelin, and 

 did not appear in the original "Handbook of Chemistry," doubt- 



