Read it through once

But as perhaps fifty of these whale-bone whales are harpooned for one cachalot, some philosophers of the forecastle have concluded that this positive havoc has already very seriously diminished their battalions. But though for some time past a number of these whales, not less than 13,000, have been annually slain on the nor’ west coast by the Americans alone; yet there are considerations which render even this circumstance of little or no account as an opposing argument in this matter.