This section is from the book "The Practice Of Palmistry For Professional Purposes", by C. de Saint-Germain. Also available from Amazon: The Practice of Palmistry for Professional Purposes.
After the malformation, come, in logical sequence, the supplementary formations, or the Duplication of certain lines. These are called by the generic name Of Sister Lines, although they are but very seldom found accompanying a line along its whole course. They are more usually marked upon the Mounts which are the normal, terminal locations of these lines; and there they run along; these main lines for a little while. Full clear, readings concerning them are given in the places where they belong.
But the student must be wanted at once against the mistake of accepting as sister lines the two split halves of one line. While the sister line is always considered as an assistance to the line it duplicates, splitting, on the contrary is one of the most unwholesomely- dangerous indications the hand reveals. A magnifying glass will never fail righting the attentive student in that respect before he commits himself to the consequences of such a startling reading.
By Forks. Branches and Tassels are designated formations which partake of the nature of Splits, since they seem detached from the very substance of the Line and of the nature of Duplications as they often add to the strength of the Line which they actually enrich. Full details concerning these modifications in a Main Line are found in the chapter devoted to it. Let me simply state here thai I have systematically called Forks such branchings of a Line found at its start or termination only; everywhere else they are named Branches.