A NAM BIS. 



anl methods adopted ly tin 1 American Society of Civil Kngineeix : uv 

 closely followed. Facilities also exist for the analysis of the raw 

 materials and their actual mixture and manufacture into cement on a 

 laboratory seal* 1 . Lack of funds, however, has so far prevented the 

 testing or in\ estimation of cements and concretes except in a desultory 

 way. 



CLASSIFICATION OF MATERIALS. 



It is most essential that all rocks tested at the laboratory should he 

 analy/ed petrographically or chemically. :md properly classified, 

 otherwise endless confusion would result. 



ANALYSIS. 



The methods of petrographic 

 examination do not differ essenti- 

 ally from those generally em- 

 ployed, The laboratory is equip- 

 ped with an exceptionally good 

 microscope of the latest Fuess 

 model, which, besides the usual 

 attachments, is provided with a 

 revolving analy/er in the tube 

 for the determination of very low 

 doubly refracting minerals and a 

 Schwarzmann scale for the meas- 

 urement of optical axial angles. 

 Another important accessory i- 

 the detachable-screw micrometer, 

 movable in the focal plane of the 

 ocular by means of a drum screw. 

 which, with the most powerful 

 objective lens, records a drum 

 interval of o.nooo^O mm. 



A very important feature of 

 the microscopic work is the rela- 

 tive quantitative determination of 

 the mineral components of rock. 

 to accomplish which an ordinary 

 fixed eyepiece having a square 

 Held was divided into loo quadratic areas. With the aid of this <! 

 line Held, each square, of which is one one-hundredth of the whole Held. 

 the relative proportions of the minerals occupying the h'eld can be 

 readily determined by simply noting the number of squares covered 

 by each mineral in turn. Averages derived from numerous examin- 

 ations of this kind in various parts of the section indicate the per- 

 centage of the different minerals constituting the rock itself. 



I--,,.. KI. _c,,re drill. 



