233 



lieen kept in plass vessels. It was frequently purified l)y shaking it 

 in flasks with concentrated sulphuric acid, then washing with much 

 water. Its density at 0^, compared with that of water at 4^, was 

 13-59.578. 



III. Recently, M. Reg-nault has determined the density of mer- 

 cury prepared with the greatest care l>y M. Millon, by the calcina- 

 tion of crystallized nitrate of mercury in a porcelain retort. The 

 metal was then shaken up witli concentrated sulphuric acid, to 

 dissolve the oxide. Density of the mercury, l.S-596a2. 



Thus we find for the densities of these three specimens of mer- 

 cury : — 



I. 13-59599 ■) 

 II. 13-59578 > 13-59593. 

 HI. 13-596U2 J 



These densities may be considered as identical. 



M.M. Biot and Arago found the density of mercury, 13-588595. 



This density differs but little from those which w'e have found. 

 The little difference ought probably to be attributed to ttie uncer- 

 tainty of the corrections which these illustrious physical philoso- 

 phers were obliged to make in their method of operating. 



It is often necessary, as in measuring heights by the barometer, 

 to know the ratio of the density of mercury to that of air. 

 Now 1 lit.of air at 0°, under a pressure of 700 mil., weighs l-293187gr. 

 „ water at its maximum density weighs 1000-000000 „ 



„ mercury at 0° „ 13595-93 „ 



The ratio of the densities of mercury and air at the temperature 

 0^, and under the pressure of 760 mil. observed at Paris, is then 

 10513-5. At the level of the sea, and in latitude 45°, it becomes 

 10517-3; and at the level of the sea, at Philadelphia, 10527-735. 



CTo be continued. J 



CONTRIBUTIONS TO RAILWAY STATISTICS, 



In 1846, 1847, AND 1848. — By Hyde Clarke, Esq. 



(Continued fvom page 245.J 



No. III.— COAL TRAFFIC. 



Coal traffic is one of the largest and most important items of 

 railway transit ; but here, as elsewhere, the returns published by the 

 Railway Department are insufficient to show the whole amount. 

 This is the more to be regretted, as the great reduction in the price 

 of coal by railways has largely increased the demand for household 

 use, as well as for manufacturing purposes. The monopolies of the 

 canal proprietors, and of the wharfingers connected with them, have 

 been broken up, and each year some new operation throws open a 

 fresh district. 



Coal traffic is of three kinds : from the colliery inland ; from the 

 colliery to the sea ; and from the sea-shore inland. 



The following shows the gross tonnage of coals, coke, and culm 

 on the undermentioned lines for the years ending 30th June, 1846 

 and 1847, 



The quantity enumerated amounts to about 8,900,000, or nearly 

 9,000,000; the number enumerated in 1845 being 7,000,000 tons. 



The amounts received for the carriage of coals in the years end- 

 ing June 30, 1846 and 1847, were as foUows: — 



Name. 



Arbroath and Forfar, . . 



Ardrossan, .. .. 



Ballochney, 



Bodmin and Wadebrldge, 



Caledonian (Glasgow and Garnkirk) 



Chester and Birkenhead, 



Cockermoutb and Workington, 



Dunfermline and Charlestown, 



Dundee and Arbroath, .. 



Durham and Sunderland, 



Eastern Counties : Cambridge, 

 „ Colchester, 



„ Eastern Union, 



„ Ipswich and Bury, 



„ Norfolk, 



East Lancashire, 



Edinburgh and Dalkeith, 



Glasgow and Greenock, 



Great North of England, 



Hartlepool, 



Lancaster and Carlisle, 



Lancashire and Yorkshire, 



„ Preston and Wyre, 



„ Manchester and Bolton, 



Llanelly and Llandllo, 



London and North Western (Birmingham 

 „ (Grand Junction) 



„ (Manchester and Birm.) 



London and Brighton (Brighton) 

 „ „ (Croydon) 



Manchester and Sheffield, 



Maryport and Carlisle, 



Midland, 



„ Bristol and Birmingham, 



Middlejhorough and Kedcar, 



Newcastle and Carlisle, 



Newcastle and Berwick (North Shields) 



Newcastle and Darlington, 



