I recieved last night your favor of May 27. and am very thankful to you for the kind offer of your odometer, on which according to the description of it I should certainly set great value. my wish to recieve it here was that I might take the distances on my road to Monticello, to which I shall go about the 20th. of the next month, and about the last day of that month proceed on to Bedford. I shall recieve you with great pleasure at Monticello, where I have probably the most powerful magnet in the US. which may answer the purpose you are at a loss for with respect to your magnetic needle. the ascertainment of the longitude by lunar observations at sea is now rendered so practicable & accurate, that any other mode must offer great precision to prevail in a competition against the lunar method. your method will therefore have a claim to the higher merit if it should be found preferable. on land, the observation of the eclipses of Jupiter’s satellites answer perfectly for the ascertainment of longitude. I salute you with esteem & respect.