The construction and operation of a new calorimeter are described. The advantages of this calorimeter are its versatility, simplicity, and ease of operation. This calorimeter can be designed and constructed in less than one day and it allows for the measurement of heat capacities while either heating or cooling a sample through a temperature interval without the restriction that the sample temperature deviate only slightly from the reservoir temperature. The calorimeter described here has primarily been utilized in the temperature range from 0.4 to 10.0 K; however, the useful temperature range is not limited to this interval. Thus far heat capacities of approximately 5 μJ/K have been resolved, but estimates indicate that heat capacities on the order of 0.1 μJ/K could be measured with this type of calorimeter.