66 
REFRAC TION. 
fessor Vince. I allude to those in which the ohject 
has a three-fold representation. The single repeti- 
tion was visible all around us ; the secondary or in- 
verted image sometimes ahove and sometimes helow 
the primary. But it was not uncommon to see, also, 
the uplifted iceberg, with its accompanying or false 
horizon, joined at its summit by its inverted image, 
and then, above a second horizon, a third berg in its 
natural position. Professor Agassiz has described a 
similar class of repeated images upon Lake Superior, 
limited, however, to two — one inverted, and above that 
the same erect. He suggests that it may be simply 
the reflection of the landscape inverted upon the sur- 
face of the lake, and reproduced with the actual land- 
scape. The calm, reflecting surface of the ice lahes 
of Baffin's Bay would favor such an explanation. The 
extension to a third and fourth image is very interest- 
ing. I am afraid to attempt delineating it. 
July 5. Although the next day was nearly calm, 
the water was so smooth, from the protection of the 
"floes," that, with hardly any perceptible motion, we 
managed to fan along at a rate of two knots an hour, 
our sails flapping all the time lazily against the masts.. 
The sailing of these ice-environed waters is incompa- 
rable in its way. The sea swell, arrested by success- 
ive break- waters, does not reach them. We sailed as 
though upon a placid lake, towed by invisible hands, 
and were only made conscious of motion by the chan- 
ges of the icy pack whose margin we were skirting. 
Toward the close of the day, refraction came back 
to us. I see by my journal that I spent four hours 
upon deck, taking sextant observations with Mr. Lov- 
ell. No fata morgana nor tropical mirage ever sur- 
passed the extraordinary scene of this night. 
