Because of the experimental difficulties imposed by the prominence of delayed elastic and viscous effects, little investigation has been made of the instantaneous elastic modulus of soda‐lime‐silica glasses above approximately 500°C. The method described in this paper provides a means of measuring the Young's modulus of such glasses. The method is applicable from room temperature to 680° or 700°C. The sample, a cylinder of glass encased in a thin‐walled metal tube, is mounted vertically in a furnace and bent as a cantilever beam by horizontal application of load at the top of the sample. The instantaneous deflection of the composite rod is measured and recorded by a suitable extensometer and oscillograph circuit. Young's modulus is calculated from the difference between the load‐deflection characteristics of the composite sample and those of an empty tube of the same metal. Data are presented for three soda‐lime‐silica glasses in the rang