152 ANNUAL OF SCIENTIFIC DISCOVERY. 



talus of the cliff on the shore, represented in inverted picture. The im- 

 age seen at the summit was probably that of a conical peak in the rear 

 of the cliff, represented inverted over the Cape. Turning away from 

 this phantom for a while, when we looked again the anvil-horn had 

 been removed, and the figure over it was gone ; but it soon reappear- 

 ed as before, and for several days we were gratified \vith a view of 

 these singular and interesting appearances, which seemed like the 

 changes of the magic-lantern. Occasional rumblings of distant thun- 

 der came to us from afar, though no storm visited us. 



" Not among the least curious and important refractions are those 

 produced on the rays from the celestial bodies. At times the sun 

 yields to the strange refractions, produced by the atmosphere over this 

 great lake, and as he draws near to the horizon expands his broad 

 cheeks most good-naturedly, or sends out a long pear-shaped neck to- 

 wards the horizon. Dr. John Locke took many sketches of the re- 

 markable forms assumed by the sun, and will probably give some ac- 

 count of his observations. The afternoon observations for a time 

 were found to be much affected by the unusual refractions of the at- 

 mosphere of the lake, and evening observations of the stars were 

 found to be utterly useless. Only stars of very high altitude, such as 

 could not be reached by the sextant with an artificial horizon, can be 

 employed for determination of latitude and longitude. This was 

 proved by numerous trials. The morning observations were found to 

 be more reliable, and were exclusively used in our determinations of 

 longitude. It is probable that this extraordinary refraction is limited 

 to the vicinity of the lake. It may be worth while to endeavour to ex- 

 plain the curious phenomena which I have described, and to account 

 for the strange antics performed by the woodland scenery of the lake 

 coast, and of the inverted image of the fisherman's boat as observed. 



"Lake Superior, being an inland ocean of fresh water in a high 

 northern latitude, (between 46 and 49 north,) has a nearly uni- 

 form and constant temperature, probably not far from the mean tem- 

 perature of the climate. It ranges from 37 to 42 Fahrenheit, never 

 rising above the latter temperature excepting in shallow places near 

 shore. The average depth of the lake is estimated by Bayfield at 

 900 feet. Its height above the sea is 600 feet ; hence its bottom is 

 300 feet below sea level. The shores of this lake are much more 

 elevated than those of the other great lakes, and high table-lands ex- 

 tend far back into the interior, and are thickly wooded. The coast, 

 especially on the north side of the lake, is abruptly precipitous di- 

 rectly to the water's edge; and the air on the surface of the lake 

 rarely is of a higher temperature than 50, while that in the forest 

 at noon is frequently as high as 90, or even 94. It is obvious, 

 then, that during a summer's day the air in the forests becomes high- 

 ly rarefied by heat, and takes up a proportional quantity of water in 

 the state of invisible moisture. When this current of warm air 

 slides from the precipices, over the surface of the lake, the warm air 

 by its specific levity from rarefaction floats upon the cooler air of the 

 lake, and does not directly mingle with it. The consequence neces- 

 sarily is, that a Jilm of moisture is condensed at the surfaces of contact 



