860 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



can be explained, and no farther. A man wlio writes his signature 

 frequently falls into a series of rhythmical movements which are pecu- 

 liar to himself. This may arise from habit or individuality of mus- 

 cular organization. His general handwriting may differ in style from 

 his signature, but the accentuation remains the same. A. talented 

 imitator may produce this general rhythm of a signature, and cause 

 the testimony of an expert to become vague and uncertain. The expert 

 may detect a difference, empirically, but he is unable to explain it to 

 the satisfaction of a jury. ' It is just at this point,' says the writer, 

 quoting from a letter to the ' New York Times,' ' where the methods of 

 the expert break down, that the more delicate methods of optical 

 analysis represented by the compound Microscope interijose to detect 

 and demonstrate forgery.' In addition to the larger rhythm upon 

 which the expert bases his judgment there is a minute secondary rhythm 

 caused by the action of the small muscles in regulating the amount of 

 pressure upon the pen, which is imperceptible to the naked eye, and 

 cannot be accurately determined with a simple magnifier, but which is 

 easily discerned in a compound instrument under a power of aboixt ten 

 diameters, if the writing is strongly illuminated with a good bull's-eye 

 condensing lens.. These variations of pressure are between 200 and 

 yOO to the inch, and are as regular in proportion as they are spon- 

 taneous and involuntary. When a man writes naturally, the pressure 

 variations are rhythmical, while on the contrary, when he is consciously 

 imitating the writing of another, they are irregular and unsymmetrical. 

 No matter how cleverly a signature may be imitated, so long as the 

 writer exercises the voluntary control of the hand, which is essential 

 to the act of imitation, just so long the margin of the stroke can be 

 demonstrated optically to be irregular in the length and the distribu- 

 tion of the waves which indicate the muscular impulses. Thus the 

 compound Microscope determines the issue at the point where the 

 coarser processes of the ordinary expert fail. My attention having 

 been called to this subject, I instituted numerous experiments, which 

 have convinced me of the general accuracy of the article, of which the 

 foregoing is an abridgment. Careful investigation enables me to 

 classify the phenomena of handwriting, especially signatures, as 

 analyzed by the compound Microscope, as follows : — 



(1) The rhythm oiform, dependent on habit or individual organi- 

 zation. This is the main dependence of the ordinary expert. It may 

 be determined by the naked eye or a hand-lens, but is still more easily 

 seen by means of the magnified image in the comjiound Microscope. 

 In some cases an enlarged photograph of genuine and disputed 

 signatures may be useful — remembering, however, that the form of 

 letters may change from time to time more readily than the general 

 rhythm. 



(2) The rhythm of progress. This is the involuntary rhythm 

 referred to above as pressure-variations on the point of the pen, and 

 seen as a wavy margin to the letters of signatures when well illu- 

 minated on the stage of the compound Microscope. It is caused in all 

 probability by the rapidly successive nerve -impulses upon which the 

 contraction of the muscles depends. In age or infirmity, these impulses 



