"Every Emotion Reacts Upon the Pulse, Which Strengthens in Joy and Weakens in Sorrow, Changes with Anger and With Despair"

"The Hammering Man."
By Edwin Balmer (1883-1959) and William B. MacHarg (1872-1951).
First appearance: Hampton's Magazine, May 1910.
Reprinted in Boston Sunday Globe Magazine, April 7, 1912; Top-Notch Magazine, May 1, 1915 (as "Decidedly Odd"); Amazing Stories, March 1927; and Scientific Detective Monthly, April 1930.
Short story.
Online at The Pulp Magazine Project (HERE, 14 pages; slow-load PDF; scroll down to page 75), Wikisource (HERE, 19 pages), and Comic Book Plus (HERE, 12 pages; select pages 27 and 93 from the drop-down menu).

"The case has suddenly developed far darker and more villainous aspects even than I feared."

Chapter I: "Advertised in Cipher"

Chapter II: "The Anniversary"
Chapter III: "The Clever Pencil"
Chapter IV: "With Nerves of Steel"
Chapter V: "An Intrusion of Science"

Scientific sleuth Luther Trant is called upon to investigate what at first seems to be a simple disappearance, but before you can say sphygmograph he's confronted with a politically-motivated kidnap-and murder-plot . . .

Dramatis personae:
~ The hammering man:
  "They say he was unusually large, gross, almost bestial in appearance, and red-headed."
~ Luther Trant:
  "I have the right, Mr. Edwards, to take up or drop cases only as I myself see fit."
~ Winton Edwards:
  "Eva! You are not married to this man?"
~ Eva Silber:
  "No! Until last Thursday, when he came to the office, I never saw him."
~ Cuthbert Edwards:
  "The loud rat-tat-tat of a cane had shaken Trant's door and cracked its ground glass from corner to corner, and the door was flung open to admit a determined little man, whose carefully groomed pink-and-whiteness was accentuated by his anger."
~ The little girl:
  "But to-night, or to-morrow, he goes away for good. He have paid only till to-morrow."

Typo: "A letter is made but giving first"

Resources:

- The Russian revolution mentioned in the story was, inferring from the date of publication, the one of 1905; see the Wikipedia article about it (HERE).
- Edwin Balmer (HERE) and William MacHarg's (HERE) work was quite popular in the early part of the 20th century; Balmer's greatest fame came with When Worlds Collide (1933), crisply filmed in 1951 (HERE), which he co-authored with Philip Wylie. For more bio/biblio-graphical data about MacHarg and Balmer go (HERE), (HERE), (HERE), and (HERE).

- FictionMags's listing of the Luther Trant stories would seem to indicate that "The Hammering Man" was the eleventh of either twelve or thirteen Trant adventures.

  A few years ago The Battered Silicon Dispatch Box published The Compleat Achievements of Luther Trant, Psychological Detective (2013), with an informative introduction by Douglas G. Greene that you can read (HERE):

   ". . . what Trant (and the authors) mean by 'psychology' is one’s physical reaction in telling the truth or a lie, and upon the instruments that can measure that response.  . . .  Eventually, a great number of machines is either used or referred to in the [Trant] stories: chronoscope, galvonometer, automatograph, electric psychometer (or 'the soul machine'), sphygmograph, plethysmograph, kymograph, pneumograph. Not every reader was thrilled . . ."

- Luther Trant is an early and prime example of the Scientific Detective School, to which Mike Grost has devoted a page on his Guide to Classic Mystery and Detection megasite and where you can find a section devoted to Trant (HERE).