THE CA USE OF MIRA GE. 171 



uniting them. The blocks are burned in a kiln until their surfaces are 

 vitrified. 



Claim : A paving block or tile composed of the ingredients hereinbe- 

 fore stated, and burned until a vitreous surface is produced, with or without 

 the grooves a and channels h or either of them. — Mines, Metals and Manu- 

 factures. 



METEOROLOGY. 



THE CAUSE OF MIRAGE.^ 



Mirage (pronounced Me-razhe) is derived from the Latin miror, a look- 

 ing glass. It is the optical phenomenon by which objects are seen as if re- 

 flected from a mirror or appear suspended in the air. Sometimes the figures 

 of objects seen suspended are inverted. The facts plainly indicate that in 

 some way the atmosphere, when this phenomenon occurs, is in such a physi- 

 cal condition that it acts like a mirror. What is the cause that produces at 

 times this physical condition in the atmosphere? 



I have compared the dates of several hundred cases of this phenomenon 

 with the local condition of the atmosphere where the case has occurred, and 

 find that fully ninety per cent, of the phenomena occur under a high ba- 

 rometer, and the remainder, not exceeding ten per cent., under a low ba- 

 rometer. Not only is this the case, but the phenomenon invariably occurs 

 when there is a calm, or at most only so light a breeze as to be scarcely 

 perceptible. The calms indicate that the phenomenon occurs at or near the 

 centres of both high and low barometers. An inspection of the daily maps 

 of the Signal Service shows, that either a high or low barometer is central, 

 or nearly so, over the locality where the phenomenon occurs. These facts 

 at once point out the direction in which we must look for the explanation 

 of the phenomena. 



Those who have carefully read what-I have written in elucidation of the 

 fundamental principles of meteorology, know that I hold high and low ba- 

 rometers are electric phenomena. In short, I hold that every centre of 

 both high and low barometers is a highly charged electric point on the sur- 

 face of the earth ; the point negatively electrified under the high barometer 

 by induction acting upon and by attraction pulling down the positively 

 electrified air in the clear sky — characteristic of high barometers — and the 

 electric point in the centre of low barometer, being acted upon by induction 

 from the overhanging positively electrified cloud — for a cloudy sky char- 

 acterizes the low barometer — sends up negatively electrified air and vapor 



