NOTES AND QUEEIES. 



227 



sidered erroneous on the following grounds : — (1) he knows no section in 

 Jamaica in which the relation of the White Limestone to the Hippurite- 

 limestone is seen ; (2) the White Limestone he believes to be of Miocene 

 age ; and (3) the shaly and sandy beds represented in the section as over- 

 lying the White Limestone he considers to be undoubtedly in infra-posi- 

 tion. The author then discussed the question of the age of the White 

 Limestone, first on physical grounds, and afterwards palseontologically, in- 

 ferring that it was decidedly of Miocene date ; and in conclusion he re- 

 marked that the White Limestone had probably been deposited slowly in 

 a tranquil sea, and discussed its relation to the Tertiary beds of the other 

 West Indian Islands. 



4. " Facts and Observations connected with the Earthquake which oc- 

 curred in England on the morning of the 6th of October, 1863." By 

 Fort-Major T. Austin, F.G-.S.— Earthquakes in the British Isles attract 

 usually but little notice, owing probably to the mild form in which they 

 generally occur ; but that one treated of in this paper, owing to its greater 

 violence, aroused attention to the subject. The disturbance was said to 

 extend from a point in St. George's Channel forty or fifty miles to the 

 north-west of Pembrokeshire to Yorkshire, and the focus of the disturbance 

 to be situated near the former spot. The author brought forward a num- 

 ber of facts for the purpose of proving the intensity of the shock, the time 

 at which it occurred, the number of vibrations, their direction (which was 

 considered to be from W.N.W. to E.S.E.), and the occurrence of inci- 

 dental phenomena, and concluded by passing in review the natural causes 

 competent to produce these and other characteristics of earthquakes. 



NOTES AND QUEEIES. 



The Measurement of Heights by the Aneeoid. — The following 

 explanation of the use of the aneroid in taking heights is given by Mr. 

 Spencer Browning, of the Minories, in a pamphlet published by him. 

 His aneroids, especially his mountain- and small pocket-instruments, are 

 unequalled for finish and accuracy. 



The theory on which the measurement of heights is effected by the 

 barometer, the aneroid, or the sympiesometer, is exceedingly simple, though 

 the application of the theory depends on formulae which have required 

 mathematical skill to construct, and which include " constants " obtained 

 by delicate experiment. 



Theory. — Let m and m' be two stations on a mountain side : required to 

 find the difference of elevation between them. 



The aneroid (or barometer or sympiesometer) having been corrected for 

 the effect of temperature upon its own mechanism, shows at m the weight 

 of a column of air, having the vacuum box of the instrument for its base, 

 and reaching from m to the extreme limits of the atmosphere. Similarly, 

 an observation at in' gives the weight of the upper portion of an identical 

 column of air, reaching from m' to the limits of the atmosphere. 



Consequently the excess of pressure at m above that at m' gives the 

 weight of that part of the column which extends from the level of in to th.8 

 level of m'. 



Knowing the weight of the column, if we also ascertain the specific 

 gravity of the air that composes it, we have data for calculating its height. 



