I cannot subscribe to Dr. Freiesleben's thesis that until the French Revolution induced a change of mind there was a big gap between men of science and seamen. It may be, as he states, that ‘in the eighteenth century there was still a remarkable gap between scientific doctrine and practice’ and it would be interesting to know the causes if this were so, but in the sixteenth and early seventeenth centuries there was, particularly in England, a quite remarkable and organized liaison between scientists and seamen with the specific purpose of improving the art of navigation. The object, as Thomas Digges expressed it in 1579, was ‘to reduce Imaginative Contemplations to Practical Conclusions’; in other words, it was to make scientific discoveries and inventions to improve the accuracy of navigation. A few examples must suffice in the space available to support this statement.