96 Civil Engi,~eering.

for the month ending the 18th March, 1859 :--530 mills "and other works, and 1466 boilers, being an increase since the 22d ult., of 50 mills and other works, and 139 boilers. We have also made 230 visits and examined 667 boilers and 500 engines. Of these, two visits have been special, and one boiler specially examined, also 11 internally, and 27 thoroughly examined: 84 diagrams have been taken from 49 cylinders ; 8 diagrams fl'om 4 cylinders have been special. The usual copies, with calculations of power, consumption of fuel, and general recommendations, have been forwarded to proprietors. The number of boilers found to be defective are as under : corrosion, 20, of which 6 were dangerous ; fractures, 3 ; safety-valves overweighted and oth- erwise out of order, 31; pressure gauges out of order, 20; water gauges out of order, 17 ; iced apparatus out of order, 5; blow-off cocks out of order, 9, of which i was dangerous; deficiency of wa- ter, 2 ; total 107. 10 boilers were without glass gauges ; 28 boilers were without blow-off cocks ; 3 boilers were without pressure-gauges ; 7 safety valves had the spindles passed through stuffing boxes.

Stephenson and Alderson.*

I have waited to see whether any one would point out the fallacy of Stephenson's statement (Athen. No. 1633, p. 217,) that either iron or ice will bear a weight passing over it at a greater velocity, which it could not bear if it went slower ; and that "when it goes quick, the weight in a manner ceases." The very reverse of this is the truth, as was clearly established by the " I ron Commission," which was appointed a few years since, to inquire into the causes of the breaking down of the iron bridge over the Dee. And the principle so established is now universally acted upon throughout our railways; the speed of the trains, upon approaching bridges of any considerable length, whether of iron or wood, is usually slackened to 8, 6, or even 4 miles an hour, according to circumstances; and the same rule, viz., of going slow, and not of going quick, is always observed in passing over an Unsound part of an embankment. I was myself present at some very interest- ing experiments made by this Commission at the iron bridge of the South-Eastern Railway, near Epsom, in the presence of Lord Wrot- tesley, Sir W. Cubitt, the Astronomer Royal, and several others. Prof. Willis had contrived a very ingenious apparatus, which, fixed to the centre of one of the iron girders, measured and registered the deflection of the bridge at the passing over of any weight. An engine with a heavily-laden tender was then passed over the bridge at speeds varying from 10 to 60 miles an hour, and it was found that the greater the speed the greater was the deflection of the girder. K . A . W .

* From the London kthen~eum~ Feb, 26~ 1859.