Among the zoologists of this country I would place Mr. Dana at the head. He is still very young, fertile in ideas, rich in facts, equally able as geologist and mineralogist. When his work on corals is completed, you can better judge of him. One of these days you will make him a correspondent of the Institute, unless he kills himself with work too early, or is led away by his tendency to generalization. Then there is Gould, author of the malacologic fauna of Massachusetts, and who is now working up the mollusks of the Wilkes Expedition. De Kay and Lea, whose works have long been known, are rather specialists, I should say. I do not yet know Holbrook personally. Pickering, of the Wilkes Expedition, is a well of science, perhaps the most erudite naturalist here. Haldeman knows the fresh-water gasteropods of this country admirably well, and has published a work upon them. Le Conte is a critical entomologist who seems to me thoroughly familiar with what is doing in Europe. In connection with Haldeman he is working up the articulates of the Wilkes Expedition. Wyman, recently made professor at Cambridge, is an excellent comparative anatomist, and the author of several papers on the organization of fishes. . .The botanists are less numerous, but Asa Gray and Dr. Torrey are known wherever the study of botany is pursued. Gray, with his indefatigable zeal, will gain upon his competitors. . .The geologists and mineralogists form the most numerous class among the savans of the country. The fact that every state has its corps of official geologists has tended to develop study in this direction to the detriment of other branches, and will later, I fear, tend to the detriment of science itself; for the utilitarian tendency thus impressed on the work of American geologists will retard their progress. With us, on the contrary, researches of this kind constantly tend to assume a more and more scientific character. Still, the body of American geologists forms, as a whole, a most respectable contingent. The names of Charles T. Jackson, James Hall, Hitchcock, Henry and William Rogers (two brothers), have long been familiar to European science. After the geologists, I would mention Dr. Morton, of Philadelphia, well known as the author of several papers upon fossils, and still better by his great work upon the indigenous races of America. He is a man of science in the best sense; admirable both as regards his knowledge and his activity. He is the pillar of the Philadelphia Academy. The chemists and physicists, again, form another utilitarian class of men in this country. As with many of them purely scientific work is not their sole object, it is difficult for an outsider to distinguish between the clever manipulators and those who have higher aims. . .