On account of the renewed interest being paid to old magnetic observations, I should like to inform you that I am continuing my researches, the results of which I published in my paper, “De Isogonen in de XVIde en XVIIde Eeuw, Utrecht, 1893.”The large number of old ship journals, in the government archives at The Hague, furnished me with a thousand new declinations, which enabled me to draw isogonic maps for the period 1540–1680, given in the above publication. From journals of later date, particularly for the years 1630–1720 and of the travels from Holland to the Cape of Good Hope, also found in the government archives, I have made extracts. There are, besides still older journals there, which were not used in the maps referred to. Among others, the independent observations made on four ships that sailed in company from India to Holland in the year 1677, are very valuable.