Old books with Google

I never mentioned that apart from partial preview, Google books offers some full-text books to read and download. For, instance, here are books in math, which are out of copyright and can be read for free. Of course, most of them are old, and even ancient as, for instance, "Arithmetical Tables Fitted to the Capacity of Such as are Unskilled in the Art of Numbers" by Henry Walrond, published in 1663. The book describes how to work with numbers, add and subtract them. 

What is interesting for me is the old English, this book is written in. Previously I thought that it will be extremely hard for me to read such old printings. But, surprisingly enough, there is no big difference with the modern language. There are some funny words there, for instance "shew" and "your self", instead of "show" and "yourself".

I wonder why Google finds many more copyright-free books in mathematics, than in physics or in chemistry...