The Metropolitan Railway’s earliest carriages dated from 1863, and were similar to the GWR rigid eight-wheelers which the company had borrowed from the opening of the line. The carriages were 39′ 6″ long and 8’3″ wide, and of the eight wheels, the outer wheel sets were free to move laterally in their axleboxes, therefore brakes were only fitted to the inner pairs of wheels. A series of derailments caused by wheels lifting clear of the track, compounded by the tightening of the curvature of the rails at Mansion House in 1884 in relation to the completion of the Inner Circle, meant that subsequent batches were fitted with radial axleboxes on the outer wheel sets, but problems with binding saw these being replaced in 1868 and a pony truck fitted instead. This latest modification were successful, and further batches were ordered in 1870 and again between 1879-84.

Of course there were detail changes over the years; the famous round-topped doors with semi-circular ventilator bonnets appeared from 1868, and these enabled the doors to open in the tunnels if deemed necessary (or indeed, if by accident) without fouling the tunnel lining. Like the Midland carriages described previously, large bags for the lighting gas were originally carried in long boxes on the roof in the style of a clerestory. Early lighting gas on the Metropolitan was was town gas, and recharged from standpipes located at certain stations. This was a frequent operation because the gas was uncompressed and ran out after about three hours use. In 1876, Julius Pintsch’s high pressure gas lamp was employed on all Metropolitan stock, and the compressed gas was stored in cylinders mounted on the underframe, replenished from gas tank wagons placed at strategic points on the system.

The photo is of a Bk3rd class carriage, number 251, built as one of a Lot of 16 by Cravens in 1884, and there were no partitions between compartments.