Would it be possible for you to devote six weeks or two months to the examination of the Florida reefs and keys in connection with their survey? It is extremely important to ascertain what they are and how formed. One account treats them as growing corals, another as masses of something resembling oolite, piled together, barrier-wise. You see that this lies at the root of the progress of the reef, so important to navigation, of the use to be made of it in placing our signals, of the use as a foundation for light-houses, and of many other questions practically important and of high scientific interest. I would place a vessel at your disposal during the time you were on the reef, say six weeks. The changes at or near Cape Florida, from the Atlantic coast and its siliceous sand, to the Florida coast and its coral sand, must be curious. You will be free to move from one end of the reef to the other, which will be, say one hundred and fifty miles. Motion to eastward would be slow in the windy season, though favored by the Gulf Stream as the winds are "trade." Whatever collections you might make would be your own. I would only ask for the survey such information and such specimens as would be valuable to its operations, especially to its hydrography, and some report on these matters. As this will, if your time and engagements permit, lead to a business arrangement, I must, though reluctantly, enter into that. I will put aside six hundred dollars for the two months, leaving you to pay your own expenses; or, if you prefer it, will pay all expenses of travel, including subsistence, to and from Key West, and furnish vessel and subsistence while there, and four hundred dollars. What results would flow to science from your visit to that region! You have spoken of the advantage of using our vessels when they were engaged in their own work. Now I offer you a vessel the motions of which you will control, and the assistance of the officers and crew of which you will have. You shall be at no expense for going and coming, or while there, and shall choose your own time. . . Agassiz accepted this proposal with delight, and at once made arrangements to take with him a draughtsman and an assistant, in order to give the expedition such a character as would make it useful to science in general, as well as to the special objects of the Coast Survey. It will be seen that Dr. Bache gladly concurred in all these views. FROM ALEXANDER DALLAS BACHE. WASHINGTON, December 18, 1850. MY DEAR FRIEND,