This from
http://www.snopes.com/politics/quotes/tyler.asp
3. The quote from "Alexander Tyler" is very likely fictitious. His name was actually "Lord Woodhouselee, Alexander Fraser Tytler," and he was a Scottish historian/professor who wrote several books in the late 1700s and early 1800s.
However, there is no record of The Fall of the Athenian Republic or The Decline and Fall of the Athenian Republic in the Library of Congress, which has several other titles by Tytler. This quote has also been cited as being from Tytler's Universal History or from his Elements of General History, Ancient and Modern, books that do exist. These books seem the most likely source of the quote, as they contain extensive discussions of the political systems in historic civilizations, including Athens. Universal History was published after, and based upon, Elements of General History, which was a collection of Professor Tytler's lecture notes.
Tytler's book, Universal history, from the creation of the world to the beginning of the eighteenth century, is available for viewing and searching on-line. The complete text was searched for each of the following phrases:
Athenian Republic
democracy
generous gifts
public treasury
loose fiscal
fiscal
bondage
200 years
two hundred years
spiritual faith
In no case was text identified that was remotely similar in words or intent to the alleged Tytler quote.