I return Hooker's letter, with very many thanks.

The glacial action on Lebanon is particularly interesting, considering its position between Europe and Himalaya.

I get more and more convinced that my doctrine of mundane Glacial period is correct (350/1.

In the 1st edition of the "Origin," page 373, Darwin argues in favour of a Glacial period practically simultaneous over the globe.

In the 5th edition, 1869, page 451, he adopted Mr.Croll's views on the alternation of cold periods in the northern and southern hemispheres.