1854.] Notes upon some Atmospherical Phenomena. 49 



Notes upon some Atmospherical Phenomena observed at Darjiling in 

 the Himalayah Mountains, during the summer of '1852. — By Captain 

 Walter Stanhope Sherwill, JRevenue Surveyor. 



The Sanatarium of Darjiling situated in the lower Himalayah 

 Mountains, at an elevation of 7,126 feet above the sea, and distant 

 from the perpetual snow thirty-five miles, affords both from its 

 elevation and from its proximity to the vast masses of perpetual 

 snow and glaciers, a favourable position for observing several very 

 beautiful phenomena that occur at all seasons of the year ; added to 

 which I may mention, that the full force of the South "West monsoon 

 is felt in these mountains. The monsoon blowing over the Indian 

 Ocean and Bay of Bengal arrives at these mountains, three hundred 

 and seventy miles from the sea, loaded with moisture, and loaded to 

 such an extent as to precipitate, yearly, one hundred and thirty-six 

 inches of rain. Much of this moisture is retained by the soil and 

 forests covering the mountains, which assists in forming the pheno- 

 mena now under consideration, and which may be divided into 

 three classes. 



Firstly ; those that are caused by great cold and depend upon 

 minute crystals of aerially suspended ice for their prismatic colours. 



Secondly ; those that are dependent upon moisture for their pris- 

 matic colours, produced by the refraction of light in passing through 

 clouds, fogs or mist. 



Thirdly ; those phenomena that are caused by cold and sudden 

 blasts of wind rushing from the snows, which meeting the warmer 

 air of the valleys, or the hot streams of air that rise from the plains 

 of Bengal, serve to form clouds by condensation. 



Of the Jirst named class of phenomena I observed but two ; the 

 first was observed on the 21st May, 1852, at seven in the morning, 

 the air was pure and bracing, Thermometer 55° in the shade ; the 

 sky to the East was covered with a dappled and streaked mass of 

 cirro-cumuli and cirro-stratus, at a probable height of 20,000 feet. 

 Upon this true "mackarel sky" was depicted one of those glorious 

 corona?, only seen at great elevations or in high Latitudes. 



The weather at Darjiling had been for the whole previous fort- 



H 



