546 
DISTINCTION BETWEEN OSARS AND ICE-BORNE BLOCKS. 
zelius have done) between the osars, or coarse drift of rounded blocks, gravel, and 
the great subangular blocks which cover them. Now in examining the tracts round 
Upsala, we had no difficulty in fully admitting a fact, first pointed out by Mr. Lyell, 
that blue marine clay abounding with shells (including the Tellina Baltica) is di- 
stinctly overlaid by osars, which are there chiefly composed of sand and gravel ; 
thus proving satisfactorily that these masses were of aqueous origin. On this point 
we entirely agree with Mr. Lyell, though we differ from him as to the intensity of 
the agency employed in forming these osars ; which must, we believe, have been 
infinitely greater than that which could have ever have resulted from rivers, in a 
flat country like this, pouring their contents into estuaries and bays. 
In looking to the three osars, which extend in succession from north and by west 
to south and by east, between Old and New Upsala, we may now add, that we 
perceived what we consider to be striking evidences of the manner in which the 
subangular blocks upon their surface were accumulated. The most northern of 
these, called Tun-os, the summit of which is about 100 feet above the adjoin- 
ing flat country, is composed of sands, clays and gravel, and is about half a mile 
long. On its northern face this os is distinguished by several ledges of coarse 
shingle, which rise up over each other in converging terraces, which gradually 
diminish in area as you proceed southwards to the summit of the hill. No very 
large blocks are associated with these shingle ridges until you reach the upper- 
most or smallest ellipse, whence a shower, as it were, of large angular and half- 
rounded blocks slope down the southern talus of the os. Seeing that blocks of the 
same aspect (granite, gneiss, greenstone, &c.) w T ere similarly lodged on the summit 
and southern slopes of the next lower os, as well as on the third, or Stor-stens-kulle 
(where one of the blocks, still quite angular, is twenty feet high and upwards of 
seventy feet round its base), we naturally concluded, that these great angular frag- 
ments were dropped upon these promontories by floating icebergs. The terrace- 
within-terrace shingle on the north face of the chief os strongly corroborated this 
view ; for supposing an iceberg floating from the north, to have been arrested by im- 
pinging against this hill of gravel and sand whilst a strong current was flowing from 
that point, the first summer’s sun would naturally diminish its volume, whilst the 
force of the current would move the icy mass onwards. By the union of these causes 
the shrinkage and advance of the iceberg would proceed each season, and thus, 
by the steady action of a northern current, the ledges of shingle having been 
washed up round the northern base of the iceberg, would be left as memorials of 
