Perhaps, if the case is one of shooting, the weapon has vanished. Its discovery may lead to the finding of the murderer. In one instance where a body was found in the woods with a bullet through the heart, there was nothing to indicate who had committed the crime. The only scintilla of evidence was an exploded cartridge--a small thing on which to build a case. But the district attorney had the hammer marks upon the cap magnified several hundred times and then set out to find the rifle which bore the hammer which had made them. Thousands of rifles all over the State were examined. At last in a remote lumber camp was found the weapon which had fired the fatal bullet. The owner was arrested, accused of the murder, and confessed his crime. In like manner, if it becomes necessary to determine where a typewritten document was prepared the letters may be magnified, and by examining the ribbons of suspected machines the desired fact may be ascertained. The magnifying glass still plays an important part in detecting crime, although usually in ways little suspected by the general public. On the other hand, where the weapon has not been spirited away the detectives may spend weeks in discovering when and where it was purchased. Every pawnshop, every store where a pistol could be bought, is investigated, and under proper circumstances the requisite evidence to show deliberation and premeditation may be secured. These investigations are naturally conducted at the very outset of the preparation of the case. The weapon, in seven trials out of ten, is the most important thing in it. By its means it can generally be demonstrated whether the shooting was accidental or intentional--and whether or not the killing was in self-defence.