§I. Among the various types of nomograms that can be constructed by means of the fertile and genial method of alined numbered points,1 the one having the greatest number of applications is, undoubtedly, that having two parallel rectilinear scales.
It seems to us that many more useful applications would appear if the study of the principle upon which it is based did not constitute a great difficulty for those who do not know or do not remember the principles of Analytical Geometry; and this is true when we notice that the principle is, generally, explained by referring to a special system of parallel co-ordinates instead of the ordinary system of Cartesian co-ordinates.
In this short note we propose to show how with a knowledge of Elementary Mathematics (in which the definition of function is comprised in order to facilitate our explanation) it is possible to understand and use the above mentioned principle.
It will then be possible for all to appreciate the advantages of the modern methods and possibly lead to surmounting the difficulties met in the fundamental study of modern nomography.