The Remarkable Sunsets. 



Nature, Londpn, V'ol. 29, 1884, p. 308=309. 



011 Friday, the iith inst., the weather was very remarkable; it recalled to our 

 minds, though on a smaller scale, the storm of December 12, 1883. I" the 

 afternoon, about three o'clock, the wind arose with violence, and great squalls 

 alternated with relative calms. The movements of the clouds were also very 

 curieus. Layers of air of different elevation floated in various directions, and the 

 lower very low-hanging clouds which moved et the same level had, at different 

 points of the sky, an unequal and changing rapidity. The wind beneath was, at 

 6 p. m., west-south-west ; the lower clouds came from the west, the more elevated, 

 on the contrary, from the north-north-west, so there is no doubt that whirhvinds 

 blew that day in the upper air. The sun had set with a very fine after-glow, 

 and in the ensuing night and morning there feil, now and then, showers of rain 

 occasionally accompanied by snow and hail. Besides, the night before a magnificent 

 halo had been observed around the moon, so that the presence of ice-crystals on 

 lanuary 11, in the higher regions of the atmosphere, is certain. In consequence 

 of the low temperature, the air in those regions must have had a great density, 

 and so. apparently, there must have been a great chance that the whirlwinds on 

 Friday had moved the heavy, cold air from above downwards. 



That this was really the case seems to proceed from the fact that during 

 the night of January 11 and 12 the rain had brought down on my windows the 

 same sediment as that of December 12, though in smaller quantity. The identity 

 of this sediment with the ashes of Krakatoa will now be beyond doubt to any 

 one who has read the numerous Communications in Nature on the remarkable 

 sunsets. Why I wish to refer to this afifair once more is that at the microscopic 

 examination of the dust of January 12 I found in it a relatively great quantity 

 of complete individual crystals, partly soluble, partly insoluble, in water, which 

 had remained unobserved by me in December. 



After having scraped the dust off the window-panes and put it on the slide 

 in a drop of oil, I made a drawing of the crystals by means of the camera 

 lucida, magnifying them 400 times, as represented in Fig. 2. 



The crystals. as seen in Fig. 2(7, evidently exist in common salt: this follows 

 from their solubility in water, their crystalline form, and their reaction in the 

 flame. They are found in so great a number in the residuum of every drop of 

 rain that we come to the conclusion that these little crystals must be found as 

 such in those regions of the atmosphere where the dust is floating, the air 

 containing there hardly anything else but ice, and surely little liquid water. 



In Fig. 2 /' we see the crystals insoluble in water. They are uncoloured and 

 perfectly transparant, and may be considered to be the crystalline form of the 

 andesitous mineral of which the ashes consist for the greatcr part. 



