As we have noted, by the fall of 1776 Boston had become a better source of supply of drugs than Philadelphia, although it had been occupied by the British for nine months and Morgan had removed most of the drugs left there the previous May. This was primarily due to a single factor--the American privateer. British shipping was vulnerable to the American privateers, which were fast vessels well suited to this kind of enterprise. Well over 1,000 captures were made during the war by Massachusetts privateers alone, and the arrivals of rich prize ships at New England ports became frequent.[103] The Greenleaf ledger confirms that drugs were included in some of these prize ships. On December 14, 1776, Greenleaf records the receipt of L62 from the Massachusetts government in payment for "an invoice of Druggs taken from the prize ship Julius Caesar." Greenleaf received an even larger stock "of druggs taken in the prize Brig Three Friends" in March 1777. This was valued at over L170, and was also used by Massachusetts to pay on its account with Greenleaf, largely for outfitting its privateers.[104] On June 30, 1777, J. G. Frazer of Boston wrote Dr. Potts, still at Ticonderoga, as follows:[105] I have the pleasure to give you this Early notice of a prize ship being sent into Casco Bay last week with four tons of Jesuits Bark on board for one valuable article besides a great quantity of other stores for the British Army at New-York. Brisk Business in Boston A series of letters to Director General Potts from Apothecary Andrew Craigie, who was on a purchasing trip through New England, gives us an interesting glimpse into the situation. On August 29, 1777, Craigie wrote Potts from Springfield[106] that he had just arrived from Wethersfield where he purchased 222 pounds of bark of excellent quality. He saw it weighed and repacked, and left the necessary instructions for shipment to Albany. Having heard that "a quantity of Bark & other articles are arrived at some eastern ports" Craigie took off for Boston where he wrote Potts on September 1 as follows:[107] I wrote you from Springfield aquainting you that I had engaged 222 lb. Bark at the Price [L5 per pound] Mr. Livingston mentioned to you; it being very dear induced me to engage a less quantity than you proposed 'til I should make enquiry here. I find to my great mortification that it is 40/[shillings] less than that in Wethersfield. I wish we could get clear of that engagement, and at least think some adjustment should be made as I am informed it cost Mr. Livingston who bought it at publick sale only 3 Pounds at which price I expect to engage 1 or 200 lb. tomorrow.... In the morning I go to Cape Anne about 40 miles from this, after medicines that have lately arrived.... Recalling Stringer's long absence of the previous year, Craigie concluded: