Catalogues of sunspots have been available with useful information about sunspots or sunspot groups for approximately the last 150 years. However, the task of merging these catalogues is not simple. We suggest a method of converting the types of sunspot groups that was proposed by Cortie (Astrophys. J. 13, 260, 1901) into the well-known Zürich types of sunspot groups. To achieve this, we used the sunspot catalogue of the Valencia University Observatory (from 1920 to 1928) in addition to the descriptions proposed by Cortie. To assess the quality of this conversion scheme, the Zürich type was computed from the Valencia catalogue, and the resulting contribution of each group type was compared to what can be found in other catalogues. The results show that the proposed scheme works well within the errors that are found in the different catalogues.