An automatic microbalance suitable for recording temperature variations in magnetisation of sedimentary rock samples is described. The beam of the balance is supported by a taut suspension made up of phosphor-bronze wire. The deflection produced by a magnetic field gradient acting on a sample of about 100 mg is detected by a displacement transducer and compensated by a feedback mechanism. The output voltage is proportional to the force experienced by the beam and may be recorded as a function of temperature on a x-y recorder. The entire balance is enclosed in a vacuum system so that samples may be heated or cooled in a controlled atmosphere. The balance is capable of detecting a force of 4.5x10^-7N, and can be constructed at a fraction of the cost of commercially available microbalances.