the light off and on and focussing the lenses.

Then he took the letter to Miss Winslow, laid it flat on the
machine, switched on the light and immediately on the sheet
appeared a very enlarged copy of the writing.

"This is what has been called a rayograph by a detective of my
acquaintance," explained Garrick. "In some ways it is much
superior to using a microscope."

He was tracing over the words with a pointer, much as he had
already done with the toothpick.

"Now, you must know," he continued, "or you may not know, but it
is a well-proved fact, that those who suffer from various
affections of the nerves or heart often betray the fact in their
handwriting. Of course, in cases where the disease has progressed
very far it may be evident to the naked eye even in the ordinary
handwriting. But, it is there, to the eye of the expert, even in
incipient cases.

"In short," he continued, engrossed in his subject, "what really
happens is that the pen acts as a sort of sphygmograph,
registering the pulsations. I think you can readily see that when
the writing is thrown on a screen, enlarged by the rayograph, the
tremors of the pen are quite apparent."

I studied the writing, following his pointer as it went over the
lines and I began to understand vaguely what he was driving at.