Side chain gear

Fig. 63 Chain final-drive for an early car
Final-drive and reduction ratio by chain drive. This was an early system used on some cars. It avoided the need to machine a crown wheel and pinion to habndle high torque (difficult in the early days) and it also allowed the differential gear to be mounted on the chassis.
Chains may also break, potentially with fatal results at speed. See Babs
Scans from 'The Book of the Motor Car', Rankin Kennedy C.E., 1912

See other images from this source in Scans from 'The Book of the Motor Car'