Correspondence. i q e 
principles;" where we find elevation in one place contemporaneous 
with a fall in another, these observation may be foretold by law. 
If decrease in the gulf stream however, can explain the upheaval of 
Scandinavia, it is admissible to inquire from whence can this variation 
in fiow be derived. In reply to this it can be said that the origin of 
the gulf stream is still a subject of dispute. Maury urges difiference in 
specific gravity of ocean waters, as the cause; Carpenter alleges dif- 
ference in temperature, expansion by heat and contraction by cold; 
others invoke excess or absence of saline contents from greater or less 
evaporation; Dr. Croll calls on the trade winds; Catlin uses subter- 
ranean rivers discharging into the Caribbean sea from the Andes and 
the Rocky mountains, but when we examine these supposed sources, 
we find every one to be a function of climate; any change in climate 
produces a variation in heat, expansion, evaporation, trade winds and 
rivers; therefore, no matter w^hich of the above reasons may be ac- 
cepted as the true cause of being of this stream, it follows that any 
variation in climate will produce a corresponding variation in these 
oceanic currents. We therefore, have merely to seek evidence of 
change in climate, and if this be found we have perfect right to de- 
cide that contemporaneous with this change there must necessarily 
have existed a variation in flow of the gulf stream, and consequently 
an apparent rise of some shore lines and a depression of others. 
We will now touch upon this matter of change in climate. Else- 
where I have shown that during the historic period there have been 
such changes, and that the period of vibration has been about 640 
years, confused, however, by minor periods of shorter duration; but 
to bring in all the data I have accumulated on this subject, is impos- 
sible here. I quote however, sufficient to establish the fact that there 
has been variation of climate in recent times. 
In 1561 "the vintage took place at hights of 2,000 feet on the moun- 
tains of Vivarais, where in the present century the vine no longer 
bears fruit," ("Ocean," Reclus, page 353). 
]M. Kerner estimates the retreat of the forest vegetation on the 
Alps and Carpathian mountains, as over 300 feet in vertical eleva- 
tion, during the last two or three centuries. (Ocean, p. 354.) 
"Direct thermometric observations have proved that for a century 
the cold has slightly increased at various places in Germany." 
("Ocean," page 354.) 
"Iceland and eastern Greenland have become much colder since 
the fourteenth century." ("Ocean," page 355.) 
The southern part of the Baltic was completely frozen over in the 
years 1323, 1333, 1349, 1399 and 1402. ("Ocean," page 57.) 
M. Venetz says before the loth century, the Swiss glaciers were 
larger than now, and after retreating for four centuries, they have been 
slowly acquiring their former dimensions. (Lyell's "Principles," nth. 
Vol. I, page 277.) 
For a great mass of testimony as to changes in climate during the 
last two thousand years, consult Mr. W. H. Larabee's article "Varia- 
tion in Climate," in the Popular Science Monthly, April, 1872. 
