THE RECENT REMARKABLE SUNSETS. 
177 
ON THE VOLCANIC THEORY FOR THE CAUSE OF 
THE RECENT REMARKABLE SUNSETS.* 
BY W. P. MARSHALL, M.I.C.E. 
The recent remarkable sunsets and sunrises have been so 
exceptional in character that it follows they must have had 
some exceptional cause, and the volcanic theory attributing 
this cause to the great Java eruption of the Krakatoa volcano 
in last autumn, although appearing on the first impression to 
be very wild and fanciful, has steadily made way, and has 
received increasing evidence in its support of an unexpectedly 
definite character. 
Two other causes have also been suggested for these 
remarkable sunsets and sunrises :— 
1st. The presence of an exceptionally large amount of 
moisture in the air. 
2nd. A possible meeting with a diffused mass of meteoric 
matter in the interplanetary space passed through by the 
earth in its orbit. 
There is now the means of testing these theories by some 
special circumstances attending the phenomena, which bear 
very definite evidence upon the question. 
The first consideration is that there must have been a 
reflection of the sun’s rays from some special stratum of 
material floating in the upper regions of the atmosphere at a 
much higher level than that of the clouds which produce the 
ordinary sunset effects. In those cases the sun’s rays are 
reflected from layers of aqueous vapour, or more correctly 
layers of water-dust, or minute vesicles of condensed water 
produced by currents of warmer air charged with water in 
the invisible state of vapour coming into contact with colder 
currents, and forming by condensation at their surfaces of 
contact, sheets of this diffused water-dust of very various and 
irregular densities, forms, and thicknesses. 
The main point to be ascertained for the consideration of 
the subject is the actual height in the atmosphere at which 
the reflecting surface was situated in the case of these special 
sunsets, and the principle of the calculation for ascertaining 
this is simple, and depends upon two measurements only, and 
first the actual extent of depression of the sun below the 
level of the horizon at the time of the phenomenon being 
observed. This is ascertained from the length of time that 
* Transactions of the Birmingham Natural History and Micro¬ 
scopical Society. Bead 22nd April, 1884. 
