72 ANNUAL OF SCIENTIFIC DISCOVERY. 



New Hampshire, 38 in Massachusetts, 9 in Rhode Island, 1 on Juni- 

 per Island in the State of Vermont, 11 in Connecticut, 41 in New 

 York, embracing, probably, the Lake Coast, 7 in New Jersey, 2 in 

 Pennsylvania, 8 in Delaware, 12 in Maryland, 8 in Virginia, 7 on the 

 coast of North Carolina, 5 in South Carolina, 7 in Georgia, 14 in 

 Florida, 3 in Alabama, 4 in Mississippi, 13 in Louisiana, 14 in Ohio (the 

 Lake coast), 19 in Michigan (Lake coast), 1 in Indiana, 2 in Illinois, and 

 6 in Wisconsin (of course the Lake coast). 



There are 32 floating lights dispersed along the Atlantic and Lake 

 coasts, varying in the number and character of the lamps. 



CONSTRUCTION OF THE CARYSFORT LIGHT-HOUSE. 



WE gather from a Philadelphia paper an interesting account of an 

 iron light-house now being erected off the coast of Florida. It is pre- 

 ceded by a short history of iron light-houses in general. " The tirst 

 iron light-house of which we have any account was erected in Jamai- 

 ca, in 1841 ; in 1844 a second one was erected on the island of Ber- 

 muda, and in 1846 a third was built for Ceylon. All three of these 

 were of cast-iron, and in the form of columnar towers, 80 to 90 feet 

 high. The Jamaica light-house has been severely tested by earth- 

 quakes and lightning, and remains quite uninjured after a lapse of 

 seven years, when, if the material had been brick or stone, it would 

 have suffered serious injury, or perhaps destruction. Several iron 

 light-houses have been erected on the Irish coast upon screw-pile 

 foundations. This foundation consists of a series of massive pillars 

 or piles of wrouglit-iron, each armed with a worm or screw of from two 

 to four feet diameter. These piles are screwed into the shoal or sand- 

 bank from a raft or from a temporary platform. 



A capstan being fitted on to the head of a screw pile, manual 

 force is applied, and as the men walk round with the capstan, the 

 screw is slowly but surely inserted in the sand beneath the waters. 

 W T hen a sufficient number of these screw-piles are thus inserted in 

 symmetrical order, and the heads of the piles framed together, it is 

 evident we have obtained a footing or foundation on the shoal, which, 

 while possessing enormous strength (from the nature of the material 

 employed), offers but a very small surface of resistance to the waves 

 as they dash furiously through this apparently frail structure, and 

 on this foundation we may erect a superstructure suitable in all re- 

 spects for the purposes of a light-house. 



A screw-pile foundation for a light-house was constructed last 

 summer (1848) on the Brandy wine shoal, with entire success, and 

 withstood uninjured the effects of the vast fields of ice that formed in 

 Delaware Bay last winter, and that must have been driven against the 

 piles with prodigious force. 



The Carysfort light-house is modelled on the plan of the screw- 

 pile at least in respect to its foundation, which consists of nine piles of 

 iron, arranged upon the angles and centre of an octagon. The in- 

 tended site for this light-house is a coral reef, where the use of screw- 

 piles would not be practicable, and where it becomes necessary to bore 



