Does "That you run up a mountain like a cat" mean "that you are so impressive"?

Context:

Relationship with Darwin[http://en.wikipedia.org/w/index.php?title=Asa_Gray&action=edit§ion=2 | editbeta]

Gray and http://en.wikipedia.org/wiki/Charles_Darwin met at http://en.wikipedia.org/wiki/Royal_Botanic_Gardens,_Kew, introduced by http://en.wikipedia.org/wiki/Joseph_Dalton_Hooker. Darwin then wrote to Gray requesting information about the distribution of various species of American flowers, which Gray provided, and which was helpful in providing information for the http://en.wikipedia.org/wiki/Development_of_Darwin%27s_theory. This was the beginning of an extensive lifelong correspondence.
Gray, Darwin and Hooker became lifelong friends and colleagues, and Gray and Hooker conducted research on Darwin’s behalf in 1877 on their Rocky Mountain expedition. After Hooker returned to England and reported to Darwin on their adventure, Darwin wrote back to Gray: “I have just...heard prodigies of your strength & activity. That you run up a mountain like a cat!”^[3]