A dew‐point apparatus for use in agricultural climatology

In connection with a study of the development and survival of the free‐living stages of sheep roundworm parasites under natural conditions, it became necessary to determine the relationship between the relative humidity of their environment and the viability of the preparasitic stages. Since this involved the measurement of the humidity of a small volume of stationary air in a closed container, the dew‐point method was adopted. As is well known, it is difficult with this method to decide visually when the dew is first deposited. Consequently, the following method of determining the dew‐point objectively was developed.