No need to change words without typos.
Thank you.
If possible pronounce "a" instead of "ei".
641 All the early vessels which have been unearthed in this part of the country have the marked lines of the potter's wheel.
642 It is not certain when the invention took place or who was responsible for it.
643 We are now unable to say how the discovery of heating food to keep it from going bad was made.
644 Nobody has any idea of the time from which this art has been handed down.
645 It is said that Egyptians were the first men to make a division of the year into twelve months.
646 It is said that the invention of the first paper of which we have any knowledge was made in Egypt.
647 The hollow stems of a river plant were pointed to make the first pens.
648 What was most important to early men was that they had come to have words for things and acts.
649 What is important with Shakespear is how the material for his plays was changed by a great mind.
650 The song is still on the lips of persons wherever they have a love of beautiful verses.
I do not understand your request: "If possible pronounce 'a' instead of 'ei'."
Do you mean the article "a", such as: a tree, a car, a boy?