BIOGRAPHICAL SKETCH OF ISAAC LEA, LL. D. XLVIl 



Academy of I^atural Sciences, to which he was a constant contributor 

 for more than twenty years, until 1877, when a sudden ilhiess, which 

 overtook him in Southern California, prevented his usual activity. He 

 was still able, however, to continue adding to his vast collection, through 

 the kindness of friends and by purchase, of fine specimens of minerals, 

 particularly quarts crystals, every specimen of which he has examined 

 with the microscope, and described on the label. The inclusions, and 

 markings on the X)lanes of each, when important, are drawn and 

 stated.* 



It will be seen by looking over his bibliography that after his return 

 from abroad he was engaged in other branches of natural history. Bi- 

 ology and paleontology claimed his attention. The embryology of the 

 Unionidce was treated in an important memoir in 1858, t in which he 

 gave descriptions and figures of thirty-eight species, accurately deline- 

 ated by himself and formed into groups. Some of these species present 

 the most singular and interesting microscopic forms, showing characters 

 which Poli, Cams, and Pfeiffer, in the few which they had given, had 

 overlooked. 



Among other works he published in 1854 his elephant folio edition 

 of " Foot-Marks," near Pottsville, which as a specimen of the typographic 

 and lithographic arts has no superior, and the importance of the dis- 

 covery of the " foot-marks " will be understood by a few extracts from 

 the many letters he received on its publication. The following are from 

 Professor John Phillips, of Oxford (of the chair of the celebrated Dr.- 

 Buckland), from Rev. Adam Sedgwick, and other friends : 



Oxford, Novemler 6, 1855. 

 * * * I am oreatly delighted with the admirable drawing and descriptiou of the 

 foot-prinls which you have kindly presented to me. 



It is unique in the beauty of the execution and characteristic of the generous spirit 

 which is so common among your countrymen, so far as I know them by their welcome 

 visits here. 



Pray send over as many of your friends as you can to maintain amity between Old 

 aiud New England. » * * 



JOHN PHILLIPS. 



CAiMBniDGE, April 13, 1856. 



My Dear Sir : I have this moment received your very kindletter, for which I re- 

 turn you my best thanks, and I am very grateful to you for the work to which you 

 allude, " The Fossil Foot-Marks"." 



My health is at present anything but good. I am the victim of suppressed gout, 

 which destroys my power of work, and makes even an ordinary task irksome to me. 

 I will write immediately to my London publisher and request him to send yon the 

 second fasciculus of the Cambridge work through the agent of the Smithsonian Ins'i- 

 tution, my friend Rev. H. Stevens. My head is in too much confusion for any en- 

 larged discussion, but I agree with you about the dithcultios of the Old and New Red 

 Sandstone. 



*Prof. H. Rosenbusch says in his Mikroscopische Physiographio der Wichtigen 

 Mineralien : "I3r. Lea was the iirst in Amciica. to enter into 'iuicroscopic mineralogy.'" 

 t Journal of the Academy of Natural Sciences, Philadeljjhia, Ittod. 



