We illustrate a high speed engine and dynamo constructed by Easton & Anderson, London. This plant was used at the Royal Agricultural Society's show at Doncaster in testing the machinery in the dairy, and constituted a distinct innovation, as well as an improvement, on the appliances previously employed for the purpose. The separator, or whatever might be the machine under trial, was driven by an electric motor fed by a current from the dynamo we illustrate. A record was made of the volts and amperes used, and from this the power expended was deduced, the motor having been previously carefully calibrated by means of a brake. So delicate was the test that the observers could detect the presence of a warm bearing in the separator from the change in the readings of the ammeter.