248 *^^ ^^^ -^N® SOUNDIJJa MACHINE. 



impression, the friction in Massey's patent lo^ is reduced to 



almost nothing by the following simple contrivance. The 



whole log, consisting of the register, a, connecting cord, c, 



and the rotator, b, is committed to the water, by a log line 



of sufficient length to reach beyond the eddy of the vessel's 



wake. As the ship moves forwards, the rotator, and cord, 



c, between it and the register, revolve and set the wheels 



into motion ; nor has the roughest sea been found to prevepi. 



this action. 



Rotator always 'Yhe rotator also, in this loff, is so constructed as always to 

 horizontal, , . , ..... , •, r ^ 



preserve a honzontal position, by being made nearly of the 



same specific gravity as water; which is effected by means 

 of an air tube passing through its centre: an indispensible 

 requisite, which no former machine possessed ; and for the 

 vant of which, they could not preserve that horizontal posi- 

 tion in fast and slow sailing, which is absolutely necessary ta 

 obtain any true result. 

 and accurately Another very important improvement consists in the con* 

 ^ ' trivance for regulating the rotator, by which means every ro- 



tator revoivt's once on its axis in passing the same space: aa 

 it was found utterly impossible to construct two rotators so 

 exactly a|ike as stated by Smeaton, without means of ads- 

 justment. 



©eneral pro- To sum up the properties of Massey's patent loc, in a few 

 perties of this , -^ u iT i 



jq_ words it may be observed, 



1. It will give the true distance sailed, from steerage way, 

 to any velocity with which the swiftest sailing vessel cau 

 move. 



2. It not only gives more accurately than the common 

 log the rate of sailing, but the actual space sailed through 

 since the last inspection. 



3. It is attended with less trouble than the common log, 

 and no mistakes can possibly arise from the result it gives. 



Another ad- It remains to point out one great and desirable advantage, 



Li gmng us^a ^^^'^h may very reasonably be expected to resnit from the 



use of this log, and that is, a more complete knowledge qf 



** friction of the spindle so much, as to prevent it from beginning to 

 «« turn, till the plate had twisted the line to such a degree, that when it 

 *< did set a. going it would frequently run one hundred and fifry or two 

 *' hundred turns at once," 



*ha 



