APPENDIX. 



C. 1. 4. THE sudden and dense fogs which come on 

 sometimes seem hardly referable to any assignable cause. In 

 great cities, the fog, whatever may be its cause, aggrandized 

 and thickened by smoke, and the breath of the inhabitants, 

 often envelops the whole town in such darkness, that people 

 are obliged at mid day to go about their business by candle 

 light. Of this, I select the following instance from M. 

 Howard's Journal, which happened on the 10th January, 

 1812 : " London was this day involved, for several hours, 

 in palpable darkness. The shops, offices, &c. were necessarily 

 lighted up ; but, the streets not being lighted as at night, it 

 required no small care in the passenger to find his way, and 

 avoid accidents. The sky, where any light pervaded it, 

 showed the aspect of bronze ! Such is, occasionally, the 

 effect of the accumulation of smoke between two opposite 

 gentle currents, or by means of a misty calm. I am informed 

 that the fuliginous cloud was visible, in this instance, from 

 a distance of forty miles. Were it not for the extreme 

 mobility of our atmosphere, this volcano of a hundred thousand 

 mouths would, in winter, be scarcely habitable !" 



An account of several remarkable circumstances attending 

 particular fogs may be found in Bertholon. Elec. des Meteors : 



