262 THE FOREST LANDS OF FINLAND. 
used. In despite of all these difficulties the work advanced 
rapidly. On the 27th of May a great piece of the dyke 
broke off from the bottom with a fearful crash; it was 
believed that the whole was about to break up, or to rise 
in a mass, and the workmen fled; but soon they courage- 
ously resumed their work. Similar accidents occurred 
repeatedly ; some of the floating masses, calculating from 
the distance at which they stood above water, must have 
had a thickness of 70 feet submerged. On the 4th of June 
the tunnel, 608 feet long, was cut from end to end ; but as 
it had an elevation of twenty feet or more in the centre it 
was necessary to level it. The weather had been cold, and 
the lake had not yet risen to the level of the mouth of the 
tunnel, so they continued to lower this till the 13th, the 
day on which the flew commenced, at ten o’clock at night. 
The lake still rose for some hours; but next day at five 
o'clock in the afternoon it had sunk 1 foot; on the morning 
of the 15th, 10 feet; on the morning of the 16th, 30 feet ; 
at two o'clock that day the lengtb of the lake had shrunk 
325 toises (nearly 2000 feet), tor the tunnel, being con- 
tinually eaten away, lowered itself as quickly as the lake. 
The Drause flowed, filled from bank to bank, but without 
overflowing, and a few days more would have sufficed to 
empty the immense reservoir. 
‘But detonations in the interior of the dyke announced 
that glacions, blocks and pillars of ice, were detaching them- 
selves from the mass, through their low specific gravity, 
and were thus diminishing the thickness of the dyke on the 
side towards the lake, while the current out of the tunnel 
was eating away this dyke on the outer side, and was 
threatening a sudden rupture ; the danger increasing, the 
engineer despatched from time to time expresses to warn 
the inhabitants to keep themselves on the look-out. The 
water began to make way under the ice, sweeping along 
the stones and earth at its base under the tunnel; the 
crisis appeared inevitable and close at hand. At half-past 
four o'clock in the afternoon a tremendous crash announced 
the rupture of the ice-work ; the water of the lake shot 
