ATMOSPHERIC DUST IK THE ARCTIC REGIONS. 161 



in the great procession of icebergs coming down that coast 

 with the cold current. These bergs were exceptionally abun- 

 dant and large in 1894, and the effect of the distortions due 

 to mirage of those on the horizon was fascinatingly beautiful. 

 Distant bergs would be appearing and disappearing. Mar- 

 vellous as their shapes are naturally, they were made much 

 more so by this optical distortion, now magnified and lifted 

 to many times their real height, then flattening out again, 

 their wavy and flickering outline — bringing them into weird 

 and strange shapes — continually changing in the brilliant sun- 

 shine. Sometimes they would fade out of sight, soon to be 

 seen again peeping above the dark but capricious horizon, now 

 divided into two with a belt of dark water between and then 

 coming back to normal form or again disappearing entirely 

 below the horizon, where a ripple on the sea showed that local 

 belts of light wind broke up the unequally heated layers of air. 



The mirages of these regions are nearly always the reverse 

 of those seen on heated deserts, which I have often studied. 

 Those are in the cooler air which rests on hotter soil. These 

 are due to the warmer air resting on colder water, and the 

 most common result is a *' looming up," or bringing things 

 above the horizon which would normally bo below it. 



This pure, dust-free air and cool temperature were pecul- 

 iarly healthful. The hygienic effects were remarked by lill 

 our party, every one of whom returned in excellent health and 

 strength, save one or two cases of minor accidental bruises. 



I await with much interest fuller investigation on the at- 

 mospheric dust-phenomena of the Arctic regions. A quanti- 

 tative investigation of the relative number of particles, and a 

 comparison in this respect with the numbers found in other 

 regions, are especially needed. Fuller and more systematic 

 observation of the various related phenomena, made under 

 other conditions and at other seasons, Avould be exceedingly 

 interesting, and rich in scientific results. 



