<span>Long after the world to which it belonged has vanished, a habit of thought will live on, indelibly imprinted upon a race or nation, like the footprint of some extinct beast or bird upon a piece of stone.
The word indelibly refers to the anything that is impossible to remove or forget. It is the mark that cannot be erased.</span>
THe second sentence is using present participle because you said " I promise" not "promised". Saying promise is when you are saying it at the time and saying promised means you've already said it. Like with how you said "kissed" instead of "kiss" in the first sentence.
There is a number of words or phrases that you could use to help smooth the transition between sentence 1 and sentence 2, and here are some of them: also, in addition, additionally, furthermore, moreover, on top of that, etc. The meaning of the second sentence adds on top of the first one - so any of these transition words would be a good choice.
A to inform about the paragraph
