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ON ATMOSPHERIC WAVES. 119 
Apprenpix No. 13. 
Estimated quantity of Iron required for the construction and putting into 
* operation each mile of Railway. 
Tons per mile. Tons of Pig-iron. 
Rails, 75 Ibs. per yard .....seeseeeees sees 235 equal to 3172 
Chairs, 40 lbs. each ......... sivddane diztses DOG Aisiekscasenss 125 
Locomotive engines, 1 per mile ciscsseee 2D seveeevenees 332 
Wagons and carriages, iron-work ..00.. 20 ssssesseeeee 333 
TA gE OCG) Irautdeata nemnde sd cons. aie cebtbate UE as Pie we ncteie 
Turntables, points and sidings............ OU iiaraehs ahs 110 
Workshops ..,..+sceseserssseeeses eee AE iE) Lah Een 402 
Coke, ovens and sundries........sesesss0e. Loe ALPE 5 
Bridges, roofs, stations, &c. ..sesseeceee 380 eeseeeeeeee 404 
711 
Required to maintain the above, each year— 
Rails, chairs, locomotives, turntables, &c., 50 tons of wrought- and cast-iron, 
equal, each year, to 61 tons of pig-iron. 
N.B. ‘The above estimate has been furnished by an experienced railway engineer 
to the chairman of a railway company. The quantities are greater than are com- 
monly assigned, but an abatement of 25 per cent. would not disturb the calculation 
made by me (page 109); and when provision is made for maintaining in repair the 
railways now open, it would absorb all the iron which will probably be made in the 
next four years, to construct, at that abatement of 25 per cent., the lines now sanc- 
tioned by Parliament. 
Third Report on Atmospheric Waves. 
By Wiuu1aAM RapcuirF Birt. 
Tue two former Reports which I have had the honour to present to the Asso- 
ciation necessarily possessed a fragmentary character. Sir John Herschel, 
in his Report on Meteorological Reductions (1843), distinctly traced two 
well-defined atmospheric waves which passed over the British Isles and the 
west of Europe, one in September 1836, the other in December 1837. These 
may be regarded as the earliest instances of our detecting and clearly appre- 
hending the character of the atmospheric undulations constantly traversing 
our oceans and continents, and mark the commencement of that era in atmo- 
spheric research to which Mr. Forbes alluded in his Report on the Recent 
Progress and Present State of Meteorology, presented to the Association in 
1832, when he said, “ The great extent of country over which the accidental 
variations of the barometer take place, is one of their most striking features ; 
and in a future and more advanced state of meteorology we may be able to 
draw the most interesting and important conclusions from the great atmo- 
spheric tidal waves which are thus perpetually traversing oceans and conti- 
nents.’ 
Sir John Herschel, in the conclusion of the report to which allusion has 
been made, noticed the larger fluctuations which I had observed in the 
autumn of 1842, especially the symmetrical wave which occupied thirteen 
_ days in November for its complete rise and fall. The curves representing 
these larger undulations were appended to Sir John Herschel’s report; and 
the Association, under the direction of the Magnetical Committee and the 
immediate superintendence of Sir John, entrusted me with the further in- 
