Correspondence — Prof. T. Rupert Jones. 479 



COBEESPOUnEUCE. 



A NEW LAKE IN THE PISTOJESE MOUNTAINS. 



Sir, — An interesting example of lake-formation has recently been 

 noticed in one of the valleys of the Apennines by my friend Captain 

 Cecil Norton, 5th Lancers. The road from Florence by Pistoja to 

 Modena crosses the mountain-range at Boscolungo, where the lime- 

 stone rocks form a semicircular arc, facing the south ; and from the 

 northern side of this ridge a spur juts out towards the north-east, 

 and forms a V-shaped valley, giving rise to a small tributary of the 

 river on which Modena is situated. On the neighbouring heights 

 the snow occasionally lies until late in the year. During the last 

 summer, as late as August 25th, snow was lying near Abetone, the 

 mountain - top of Boscolungo, and about 4,500 feet high ; also 

 away eastward, on the hill-tops on the southern side of the gorge 

 beyond Monte Cimone, which is the crest, 6,700 feet high, at the 

 head of the valley above mentioned. As in the Alps and elsewhere, 

 these Italian snows are subject to sudden meltings, though it is said 

 to be fifty years since so rapid a thaw, or such a flood of snow- 

 water, has been recorded as that of this year. The mountains here, 

 it will be remembered, are composed of limestone and sandy macigno, 

 and therefore so highly susceptible of frost - action that the 

 accumulation of debris on and at the foot of the slopes is 

 often considerable. Some time in June last so sudden and rapid a 

 melting of the snow occurred as to sweep down a large mass of 

 debris, sufficient indeed to completely block the bed of the rivulet 

 above mentioned, forming one of the head-waters of the Modena 

 river. The result was the formation of a lake, some 300 or 400 

 yards long, by 150 or 200 yards wide, at the time when it was seen 

 (from the pass) on the 24th August. 



It will be interesting to notice hereafter what effect the retention 

 of the water will have on the dam of this little lake. "Will the dam 

 be violently cut through, or totally swept away, by gradually ac- 

 cumulated water ? Will it be strong enough to withstand the 

 pressure ? Will it be quietly worn down by the overflow, so as to 

 allow of the gradual lowering of the lake ? Will it be undermined 

 by the destruction of its lower part ? In any case the debris left 

 will be moraine-like in character ; and might, but for the want of 

 the regular striae, be mistaken for the results of an old glacier. 



Thus, it may be instructive to place on record this formation of 

 a moraine-like heap, which, without careful examination as well of 

 detail as of general appearance and situation, might at some future 

 time be attributed to the action of a force very different from that 

 which brought it to its place. T. Kupert Jones. 



Staff College, Camberley, 

 Sept. IQth, 1879. 



