SSA LOG AND SOUNDINft MACHINE. gA^ 



least value of m; hence all the numbers from y to y -<- 2 m 

 are properly resolved, except y + 2 m — 1. Now, let a be 

 the index, which resolves y 4- 2 m — 2 into polygons; and 

 the same, a, will resolve y + 2 /n— .1 into m 4- 1 polygons; 

 but the next value of a zz a •{• 2 — wi (cor. 1, prop. 4) ; which 

 will re!>olve y 4- 2 m — I into tw polygons, or less, (cor. 2, 

 prop. 5). In general, if ^ r: y -f f can be resolved into m 

 polygons by the index a, the next index a ■\- 'i'—'Tn, will re- 

 solve tf 4- 1 into m polygons, or less (cor. 2, prop. .5). 



JOHN GOUbH. 



Middkshawy October 15, 180S. 



II. 



^Description and Use of a Sea Log, and Sounding Machintt 

 invented by Mr. Edward Massey, of Hanleyt in SttgT* 

 fordshire. 



Tc 



O the nautical reader the advantages resulting frotij t 



log, that will give a dead-reckoning free from errour, or log wanted. 



nearly so, must be sufficiently obvious; and to others it would 



be superfluous to point them out. The principle, on which 



Mr. Massey's patent log is constructed, is not new; buteverj' 



application of it to practice has been found defective, and 



this is the difficulty the patentee has had to surmount. To 



understand the manner in which it acts, s6e PI. 7# where d, ^, 



1 ... , . , . , , New \o^ dtf-. 



fig. 1, IS that part of the log which registers the distance scribed, 



sailed, and is therefore called the register; it contains within 



itself a set of wheel work, which operates "upon tbe fingers of 



the several indices, 1, 2, and 3. 6 is the rotator, a hollow 



cylinder, made air-tight, and so nearly of the same specific 



gravity as water, as to float when drawn forwards with the 



velocity of mere steerage way. On this rotator are fixed 



four vanes placed obliquely. It is then fastened to the re« 



gister by a cord, c, about six feet long*: to the loop-hole 



• This cord is shown scarcely one tenth part of its proper length in the 

 engraving: it would have been an unnecessary extension of the plate to 

 jepresenX it otherwise, as it may so retidily be conceived. 



at 



