The appliances necessary for the work of examination are, a good magnifying or reading glass of the greatest power obtainable, a pair of fine compasses or dividers, a horn or celluloid protractor for measuring angles of slope, and a clearly marked scale rule. Suitable articles will generally be found in an ordinary case of mathematical instruments.

A simpler and equally accurate method of taking measurements of handwriting is by the aid of the transparent paper known as foreign letter paper. It is usually of quarto size, very thin and transparent, and is ruled horizontally and vertically, dividing the sheet into tiny squares. It is laid over the writing to be examined, and the various measurement marks are made with a finely pointed lead pencil. The lines and squares are used for measurement as the parallels of latitude and longitude are used on a chart. For example, a letter is said to be so many lines high, so many lines wide. One of the tiny squares should be carefully divided into two, or, if possible, four parts, so as to ensure finer and more accurate measurement. A letter may then be measured in parts of a line, being described, for example, as, height 6¾ lines, breadth 2½ lines. It is of course important that the same gauge of ruled paper be used uniformly, otherwise the measurements will vary. If the student has had practice in the use of the dividers and scale rule, he may prefer to employ these, but the ruled paper and a finely pointed lead pencil will be found sufficient for most purposes. A paper specially prepared for surveyors, ruled in squares of one-eighth of an inch may be obtained. For measuring the slopes of letters a transparent protractor is necessary. The letters measured are all topped and tailed small letters, and all capitals having a shank. Letters like O, C, Q, S, and X can only be measured approximately.

The method of applying the measurements of heights and angles of slope is shown in the case illustrated by the table on page 15.

The subject of enquiry was a signature containing the letters B, l, k, b.

The measurements of these letters in the forgery are given at the top of the table, and show the height in lines and angle of slope in degrees.

The measurements of the corresponding letters in twelve genuine signatures are shown in the table as Examples 1 to 12.

The total is averaged by dividing by twelve.

The presumption in favour of the suspected signature being a forgery is strongly supported by the arithmetical result.

A difference of more than 2 per cent. in angle of slope, and 3 per cent. in height may be safely relied upon as ground for suspicion, for it is rarely that a man's signature varies so greatly within a brief period. In the absence of the explanation provided by illness, intentional change in style or other abnormal circumstances, such a difference as is shown in this example will justify a belief that the suspected signature is by another hand.