300 Notices respecting New Books, 



radiation-thermometer at night*. With the data, however, now- 

 afforded by the experiments with screens, and the eye-obser- 

 vations of cloud with which they were associated, it cannot, I 

 think, be doubted that the peculiar stinging sensation experi- 

 enced by H. v. Schlagintweit in India (apart from the high read- 

 ings of insolation which he observed in regions of great relative 

 humidity) must have been owing to the diversion of rays of 

 small obliquity by light cloud high up in the atmosphere; 

 they consequently reached the bulb of his solar thermometer 

 almost in a direct course and with little loss of heating-power. 



I am not aware whether the fact that so great an accession of 

 heat is attributable to the near approach of light cloud to the 

 sun has previously been observed. Certainly, as regards my 

 own experience, the not uncommon sensation of a sudden in- 

 crease of solar heat under a partially clouded sky was always as- 

 sumed to be due, not to light cloud approaching the sun, but 

 to its passing off from it — or, if the sky appeared, on a superficial 

 view, to be clear and cloudless, to some possible outburst of heat 

 in the sun itself. 



The question whether the direct rays of the sun are more 

 intense in proportion as they pass through a limited extent of 

 atmosphere is scarcely an open one. But it will be seen that 

 the admission of loss of heat from absorption in no wise mili- 

 tates with the fact that a high degree of insolation may be, and 

 sometimes is obtained, even at comparatively low altitudes of 

 the sun, under atmospheric conditions which favour counter- 

 radiation, or, in the case of cloud near the sun, by complete 

 reflection of the solar rays. 



I am, 



Yours faithfully, 



Ewhurst, March 1, 18/0. J. Park Harrison. 



XLII. Notices respecting New Books. 



Our Domestic Fireplaces. A New Edition. By Frederick Edwards, 

 Jun. London: Longman and Co., 1870. (Pp. 168, with many 

 illustrations.) 

 rriHIS work has been "entirely rewritten and enlarged, the additions 

 -*- completing the author's contributions on the domestic use of 

 fuel and on ventilation." It consists of a short historical account of 

 open fireplaces, and of the various recent projects for improving 

 them. The author's principal suggestions are made under the fol- 

 lowing heads :— (1) The best form of grate should be used — that, 

 namely, which presents the largest amount of radiating or reflect- 



* Proceedings of the Royal Society, February 1867; and Phil. Mag. 

 vol. xxxiii. p. 391. 



