Arrived in the library he at once went to the desk and opening it, began to look around.
He first took out the ink bottle and carried it to the better light near the window. It was a jet-black ink of heavy consistency, showing that a considerable quantity of gum arabic had been used in its manufacture.
Finding a piece of paper on which Mr. Field had begun a letter, only to afterward cast it aside, the detective wet the writing with a drop or two of water.
At the same time he put a couple of drops on the writing of the letter received by the girl downstairs.
The ink known to have been used by Mr. Field soon began to spread, as the water softened up the portion of the gum that had dried. But, on the ink of this other letter, it had no effect whatever, showing the absence of gum.
To himself he said:
“This little test shows absolutely that these two inks are not the same. Now, then, this letter to Barnes was written only two days ago and this one to the girl is supposed to have been penned yesterday. It is hardly likely that in this interim of a day Mr. Field changed his ink. Still, as it is possible, I must inquire into the matter. It is about what I expected, and if I fail to find steel pens around his desk, I will have a clear bill.”
The most careful search of the desk failed to bring to light anything in the shape of a steel pen.
When thoroughly satisfied that there were none, the detective smiled grimly, and said:
“This proves the letter absolutely to be a forgery. It is in the writing of Mr. Field, or at least his penmanship has been so cleverly imitated as to deceive the best experts, so far as the strokes are concerned, but the villain who is so deft with the pen did not know that Mr. Field never used anything save a quill. If he had known it he would not have written this letter with a steel pen!”