34 ANNUAL OF SCIENTIFIC DISCOVERY. 



ter in this respect has made it, since the days of St. Paul, an emblem of the 

 Christian's hope. It is from its form, weight, and area alone that it derives 

 this character the "mud-hook" being one of those devices which can not well 

 be attended to and guided by hand when at work in its briny bed. The or- 

 dinary form has been found, by both theory and experiment, best adapted to 

 penetrate and hold in every variety of bottom. The flukes are armed with 

 broad, thin palms, but these can not with safety be extended beyond a certain 

 degree, from the increased liability to damage in case of being jammed and 

 twisted among recks. In short, the present anchor is a compromise be- 

 tween the forms best adapted to a rocky or tough clayey bottom and that 

 best formed to hold in a loose and treacherous earth. Mr. De Guinon's inven- 

 tion makes the anchor adjustable by adapting it to receive two very broad 

 shovel-like plates of thin wrought-iron, with convenient fastenings so that 

 they ma}- be attached or disconnected at pleasure, forming, when in place, an 

 immense scraper, somewhat resembling an expanded umbrella. The attach- 

 ments are held in place by the aid of a collar on the shank, a strap passing 

 round the point of the fluke, and by several bolts which pass through pro- 

 jecting ears on their joining edges. The place of these bolts might probably 

 be better supplied by a clip-ring as making a far stronger connection, but this 

 is all a matter of un important detail. For an anchor weighing 1,000 pounds 

 the attachments are to be f inch thick at the center, \ inch thick at the ex- 

 terior edges, and weigh, with their fastenings, 400 pounds. Several braces, 

 extending from suitable points in their surfaces to a point near the head of 

 the shank, contribute very much to strengthen the structure, and an addi- 

 tional rope or chain is attached to an eye at the crown in order to invert and 

 dislodge it, or discharge any material which it may bring up from the bottom. 

 ^ Y. Tribune. 



EXPERIMENTS WITH THE BLADES OF PADDLE-WHEELS. 



A valuable paper on the above subject has recently been published in the 

 Journal of the Franklin Institute, by B. F. Isherwood, Chief Engineer, U. S. N. 

 The proper number of paddles for a wheel has been a matter of some dispute, 

 and the question has been discussed by Mr. Ewbank, in an essay on propel- 

 lers. Tiiose who assume the position that too many paddles are generally 

 employed, base their opinions on the assumption that " every blade, according 

 to its thickness, forms part of a solid rim, and detracts from the propelling 

 efficiency of the wheel," hence they insist that the number of paddles gener- 

 ally used on paddle-wheels should be reduced. The paper referred to throws 

 light on this very point, and seems to settle the question. The experiments 

 to test the question were made on the U. S. steam frigate Mississippi, during 

 her cruise in the Mediterranean, in the years 1849, 1850, and 1851, under the 

 direction of the Chief Engineer, Jesse E. Gray. The frigate had occasion to 

 make a considerable number of short trips between Spezzia and Leghorn, a 

 distance of 37 geographical' miles. These passages were made in fine 

 weather light breezes and a smooth sea and the dip of the paddles was 

 about equal in all cases. Eixht possagos weiv made v.-irh thv usual number 



