This book is an important historical source, originally written by a man who was an eyewitness to the plague that killed 100,000 people between 1770 and 1772. Charles de Mertens was the doctor to a foundling home. There is a limited account of this plague epidemic. It is not as well-known as it should be due to politics at the time and a translation lag. Therefore this book is an important source of primary information.