当我登上HMS（英国皇家海军舰队）小猎犬号时，作为一名自然学家，我对南美州居民的分布以及那片土地从现今到过去居民的地理关系等特定事实震惊了。

H.M.S. Beagle = a ship in the Royal Navy (皇家海军). as naturalist = When he was on board the ship he was a naturalist. (Is this about David Attenborough ?)

H.M.S. = his/her Majesty's ship, the prefix of any British Royal Navy ship to show its allegiance to the monarch. As a naturalist = in the capacity of a naturalist, serving as a naturalist (someone who studies nature). to be much struck = to be shocked, to be amazed by something (archaic).

This is Charles Darwin from probably 'Origin of the Species' written about 180 years ago. This is an older style of formal English. When on board H.M.S. 'Beagle,' as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent.. I don't understand especially the words " H.M.S. 'Beagle,' as naturalist" and "much struck" H.M.S. 'Beagle was a British navy sailing ship on on a map drawing world circumnavigation around 1830's naturalist meant scientist around 1830 distribution of the inhabitants of South America - relates to evolution, Darwin observed the different species of life and how they looked like each other much struck - means surprised geological relations of the present to the past inhabitants ie he was comparing fossils to living creatures

paypal me 1 million USD and i'll do it :P