Correspondence — J. Curry. 191 



I regret to say that I am not acquainted with the examples of 

 lagoons in Ireland, to which the Fleet is supposed to be analogous. 

 Probably Mr. Kinahan's explanation of their origin may be correct : 

 but that the like will account for all the marshes and reclaimed low 

 lands from Portland to Dover seems to me highly improbable. Take 

 the same sheet of the Map, and observe the forms of the indentations 

 of Weymouth Backwater, and of Lodmore ; or further east, of Poole 

 Harbour, Southampton Water, Portsmouth Harbour, Langston and 

 Chichester Harbours. The action of the sea upon a coast composed 

 of soft strata cannot possibly have formed these indentations. They 

 must be drowned valleys. 



I feel much supported in my views about the Fleet by the corro- 

 boration Mr. Mellard Reade has given to them.* 0. Fishee. 

 Harlton Eectory, near Cambeidge. 



STALAGMITIC DEPOSITS. 

 Sir, — When the organic remains which are found buried in caves 

 are receiving such general attention, and when attempts are being 

 made to determine their age by the rate of stalagmitic deposits, I 

 trust that the following case of such deposits may be of interest to 

 the readers of the Geological Magazine. 



About 30 years ago, I procured a piece of lime deposit from a lead 

 mine at Boltsburn, in the county of Durham. It measured 18 inches 

 in length, 10 inches in breadth, and fully | of an inch in thickness. 

 It was compact and crystalline, and showed distinct facets of crystals 

 on its surface, over which the water was running. I have indisput- 

 able evidence that the deposit had been accomplished in 15 years. 

 The water from which it was produced issued from an adit driven 

 in the Little Limestone, which is about nine feet thick. After 

 leaving the adit, the water ran down the perpendicular side of a rise, 

 for some fathoms, on to some rock debris, which was lying on the 

 bottom of a hopper, whence it proceeded from the upper part of the 

 hopper mouth, then perpendicularly downward over two narrowish 

 wood deals, which were set on edge, and put across the mouth of 

 the hopper to stop the marked materials. IL was from off these deals 

 that I obtained the specimen above described. On its under side the 

 forms of the deals were well defined ; on the exposed surface, the 

 crystals were best developed where the stream was most active. 



In accordance with the above rate of increase, namely, f of an 

 inch in 15 years, 5in. would require 100 years, 4ft. 2in. 1000, and 

 41ft. Sin. 10,000 years. The data here given to arrive at these 

 results may be relied on as being accurate. In the case now related, 

 the rate of increase was likely to continue tolerably uniform, as 

 the surface water could have no appreciable influence in augmenting 

 or lessening the flow from the adit. John Curky. 



Boltsburn. 

 Explanation of terms, if required.— h. "rise" is an excavation made by the miner 

 working from below upwards ; size, generally about 9ft. by 4ft. A " hopper" is made 

 by bratticing (or partitioning) off a portion of the rise, and putting timbering hori- 

 zontally across the low part for a bottom ; its use is to hold the worked materials. 

 1 Geol. Mag. Vol. X. p. 573. 



