4 October: In the morning, bright sunshine; the weather has cleared up. Work on the animal drawings was continued. At ten o’clock Dr. Saynisch visited a professor of chemistry, Mr. Peter, who owns several natural history specimens, and a Mr. Graff, who has a fine shellfish collection. At noon There are said to be sixty to seventy varieties of freshwater shellfish west of the Alleghenies. In his work with colored illustrations, Lea describes fifty-four species of the genus Unio.M13Observations on the genus Unio, together with descriptions of new genera and species in the families Naiades, Melaniana, and Colimacea, by Isaac Lea. Philadelphia 1832. Printed by James Kay, Jun. and Company. Printed to [sic] the Society. According to Mr. Say, who is unquestionably the best-informed expert on American Testacea, there are many errors in this book.

Dr. Saynisch had collected about twenty species near Pittsburgh, including the following: 1. Unio rugosus; 2. aesopus; 3. occidens; 4. abruptus; 5. irroratus; 6. orbiculatus; 7. gibbosus; 8. cylindricus; 9. praelongus; 10. scalenius; 11. torsus; 12. ellipticus; 13. Anodonta areola; 14. cuneatus; 15. mytiloides; [and] 16. alatus.M14According to Mr. Say, some of these names are incorrect, since many of the conchylia named by Mr. Lea had been described earlier.

We let the magnetic needle oscillate, and it gave us 142 1/2 oscillations at twelve noon. Dreidoppel was suffering from severe toothache. The magnetic stroke, which helped immediately in Bethlehem, has no effect here.