Good Friday in Melbourne was marked by a most painful occurrence, six men losing their lives in a tunnel which is being made under the Yarra, near Spottiswoode, in connection with the metropolitan sewerage works. The task of tunnelling under the bed of the river has proved a most difficult one. The borings made into the bed of the stream before the works were let indicated that sound and easily-worked material would be encountered. A shaft was sunk 61ft, and then the work of driving a tunnel lift in diameter was undertaken. The ground proved to be sandy and treacherous, and it was found that all the resources of engineer ing would be required to carry the work to completion. Wheu about 400ft of the tunnel had been driven, an air-lock was constructed. This consists of a strong brick chamber built across the tunnel, into which compressed air is pumped from an engine on the surface, and compressed air is also supplied to the face beyond this, in which the men work. The compressed air is used to hold up the face of earth and to keep the water back, and the air lock is used to allow transit from the shaft into the face where the men work. When the pres sure of air in the lock equals that in the face the door between the two opens. When it is necessary to pass from the air lock back to the shaft the iron door communicating with the face is closed and the pressure is thus maintained there. The men work inside an iron shield, which is driven for ward by hydraulic pressure. Inside this shield a casing of iron is constructed in sec tions of 2ft 9in at a time, and inside this there is one foot of brick and cement built. At three o'clock on Good Friday afternoon five men went on shift, and Mr Buchanan, the engineer superintending the works for Messrs Robb and Co., was with them nearly the wholeof the afternoon. At half-pastseven Henry Hoard, a fitter, who erected the iron plates into their position, left the face where the men were working, and passed into the air lock in order to get a further supply of plates. Mr Buchanan was then with the men in the face. 