Thanks for your response, George, and very interesting articles by Deb and yourself. I had read previously about the suspicions of the explosion on the SULTANA being as a result of secret service activity, but the information on the MARIA was new to me. Understandably so, since my main area of interest is in the Navies, and not much on the transport and other vessels belonging to the Union Army.
The letter in the collections of the Chicago Historical Society contains an admittance by Courtenay that it was his own invention that was responsible for the explosion on the USS CHENANGO (I have not come across a photo of this Union Navy vessel at all), and this was written about three weeks after the explosion. Tom Thatcher has indicated that Joseph Thatcher holds other letters of Courtenay's written at a later period, also admitting that the "coal torpedo" was responsible for the explosion.
Deb Rule's intimation that these devices were probably responsible for a lot more damage than what we currently believe, is almost certainly correct. The evidence would have been destroyed in the explosions, and much suspicion would have fallen upon faulty boilers, etc. The well known explosion at Grant's supply base, at City Point, was another one that was believed to have been caused by such a device.
Unfortunately, because of the purposeful destruction of many of the Confederate secret service records at the close of the war, we will probably never know the full extent of the damage caused by these inventions. Perhaps more will come to light through letters and journals, as well as other official CS documents held in private hands, handed down through the secret service operatives themselves.
I think researchers such as you and Deb, as well as Tom and Joseph Thatcher, are doing a commendable job of trying to locate such material, and placing the evidence before the lay person. I am sure that there is much more to be found in the future.
I have not seen the Scientific American article, nor the Porter book you mention. Please let me know the titles, and I will obtain copies through some means or other.
I am currently awaiting copies of the Inquiry report into the explosion on the CHENANGO, as well as other related documents. Hopefully this will shed more light on the explosion and it's aftermath.
Courtenay mentions that he had 20 or more operatives who planned to cause havoc with the "coal torpedos," and if we could locate the names of all these operatives (Tom sent a copy of another document showing the names of four of them), perhaps more manuscripts could be located relating to the Confederate secret service. Authors William Tidwell, James O. Hall and David W. Gaddy have also done some work in this area, and I believe that they may have located some documents relating to the CS secret service in general, but not particularly on Courtenay and his "coal torpedo."