392 Scientific Intelligence. [May, 



Article XIV. 



SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. The Logan Stone in Cornwall overturned. 

 (To the Editor of the Annals of Philosophy.) 

 DEAR SIR, Plymouth, April 18, 1824. 



Your geological readers will hear with infinite regret, that the cele- 

 brated Logan Stone in Cornwall, which has for so long a period been 

 regarded as an object of great national interest and curiosity, and which 

 has been visited by persons from the remotest extremity of Europe, 

 has within the last few days been overturned by one of the Lieutenants 

 of his Majesty's navy, noiv commanding a revenue cutter, stationed 

 between the Lizard and Lands End, assisted by a party of his men. 

 The barbarous and wanton folly which could induce an officer bearing 

 his Majesty's commission to commit so unwarrantable an act, as to 

 remove a great national curiosity from a position in which it had stood 

 for ages, defying the hand of time, and affording to the enlightened 

 traveller an object of such singular interest, will, it is hoped, be visited 

 with the severest displeasure of the Admiralty. In a tour through 

 Cornwall in the summer of 1821, I was informed by a cottager who 

 lived near the spot, that an attempt was made by a party of seamen 

 some years before, to remove it, but without success. Cornwall, by 

 this wanton outrage, has lost one of its most interesting monuments. 

 I remain, dear Sir, yours very truly, G. W. Harvey. 



II. The Rate of a Chronometer varies with the Density of the Medium 



in which it is placed. 



Mr. Harvey, ERSE, has lately discovered that the density of the 

 .medium in which a chronometer is placed, has a sensible influence on 

 its rate, in most cases producing an acceleration, when the density is 

 diminished, or a retardation, when the density is increased. In a i'ew 

 time-keepers he has found the reverse to take place, viz. a decrease of 

 rate from diminished density, and an increase from increased density ; 

 but the former appears to be the most general effect. Mr. Harvey 

 has proved this to be the case, by an extensive course of experiments, 

 and in which he has subjected many chronometers to pressures, from 

 half an inch of quicksilver to 75 inches; and in all cases has found, 

 that if a time-keeper gained by increasing the density, it lost by dimi- 

 nishing it, and vice versd. A difference of density denoted by an 

 inch of quicksilver, is sufficient to produce in many chronometers a 

 visible alteration of rate. 



The following are a few of Mr. Harvey's results : — 

 A pocket chronometer which possessed a steady rate of + 1"*6 

 under the ordinary circumstances of the atmosphere, had its rate in- 

 creased to + G''-2, when the density of the air was diminished to a 

 quantity represented by 20 inches of quicksilver ; and on afterwards 

 placing it in air. of a density denoted by 10 inches of quicksilver, a far- 

 ther increase of its rate to 4- ll"-0 took place. On restoring the time- 

 keeper to the ordinary circumstances of the atmosphere, its rate re- 

 turned to + 2"-l. 



