-We copy the following paragraph from The American Architect and Builder of February 26 ; " We would cali the attention of our readers to a series of Articles on the Graphical analysis of Roof-Triisses, by Prof. Qreone of Michigan University, which are now publishing in the Chicago Engineering News. The graphical method of solving statical problems is one which has been developed in Germany during the last ten years, and, though bronght somewhat into noties in England by Prof. Clark Maxwell's analysis of certaln roof-irusses, is only now becoming generaliy known. It has the advantage of enabling constructora who are not versed m mathematics, to determine, with 8ufficient accuracy for all practical uses, the various strains to he provided for in their constructions. And in many ' cases of complex relations it materially assists the traiued engineer by substituting a comparatively easy graphicai solution of bis problems for a laborious and abstruse calculation, - as, for mstnnce, in oomputing tlie atrains of continuous grades, besides giving an independent means by which he may check his computations when he makes them. This system was firat show in a complete form in a Germán work published by Colmanu in 1866, who developed it by means of transversals, a somewhat complicated system of enharmonic relations, lor which, by the labora of other inveatigators, a simple means of analysia has been substituted. Prof. Greene had already published aamall book on the subject, in which, however, he liraited hia discussion niainly to bridge-grades. In these papers in the Engineering News, he takes up the study of varioua forms of roof-trussea, an ill-understood subject, which is of great importance to archiiects and buildei-s, and which he treats in a way that should enable men who lck facility in computationa, but yet wish for thorough and accurately contrived work, to erect their conatructions with exact reference to the straiua they have to bear. The pressure of wind, an element in the stability of roofs whose importance is not commonly understood, is carefully studied in these papers. The subject is of such practical importance that it ought to be studied by every constructor, and must soon be mtroduced into the curricula of all our engineering and technological schools."