404 nutting: reflection ocular 



On account of the light winds that prevailed, both dust and mois- 

 ture accumulated in the atmosphere on the 10th and 11th, but 

 were swept away by the higher winds of the 12th. 



In addition, innumerable little whirls would be established in 

 a body of stagnant air that was being heated rapidly and unequally 

 from point to point on account of variations in the character of 

 the surface below. At the boundary surfaces of these whirls 

 heat and light waves would be both reflected and refracted, where- 

 by adding to the haziness attributable directly to dust or moisture 

 particles. These whirls would be most numerous at the time 

 of the most rapid rise in temperature, or from shortly after sunrise 

 to shortly before noon, and would cease before sunset. The air 

 would also be relatively drier in the afternoon than in the morning, 

 on account of its increased temperature, and in consequence the 

 dust particles would have less hazing effect. 



It appears, therefore, that the dense haze of June 10 to 11, 

 1912, may be attributed to the effects of convection in quiescent 

 air prevailing at the center of a nearly stationary center of high 

 pressure, and that the unusual diurnal variation in atmospheric 

 transparency on the 10th was the result of diurnal temperature 

 changes. 



A rapid diminition in the solar distance of Babinet's neutral 

 point occurred on both the 8th and 10th when the sun was about 

 3 degrees below the horizon, being especially well marked on the 

 10th. It therefore seems probable that the upper limit of the 

 haze on the 10th was at about the height of the top of the cumulus 

 cloud layers of the two preceding days, or approximately at 3 

 kilometers above sea level. This conclusion is in accord with 

 the results of recent studies by Suring and Humphreys. 1 



PHYSICS.— ^4 new reflection ocular. P. G. Nutting, Bureau of 

 Standards. 



The reflecting ocular here described was devised as a substitute 

 for the well known Gauss ocular to give increased illumination 



Humphreys, W. J., Dust layers in the atmosphere and changes in the neutral 

 points of sky polarization. Bull. Mt. Weather Observ., 4: 397. 



