464 



SCIENCE 



[N. S. Vol. L. No. 1298 



By obtaining a number of sueb correspond- 

 ing points, the translation curve (Fig. 2) is 

 constructed. Tractional weights being incon- 

 venient, the most practical tabulation will 

 probably be as follows : 



TRANSLATION TABLE PROM PERCENTAGE GRADES TO 

 WEIGHTS 

 Grades Corresponding Weight 



0-50 



50-51 1 



51-54 2 



54^-67 3 



67-82 4 



82-92 5 



92-97 6 



97-100 7 



100 8 



Very exceptional 9 



Practically certain 10 



This table will serve our purpose in most 

 cases. One further refinement may be desir- 

 able, especially if the observer suspects that 

 his ovm habit in grading is far from normal; 

 that is, if he is inclined to be either unusually 

 severe or unusually lenient in assigning 

 grades. The article previously referred to 

 contains tables which afford the necessary 

 correction. The writer, for example, is a 

 grader of Type 6 as there classified, and in his 

 case weight 5 corresponds to grades from 77 

 to 88, instead of from 82 to 92; etc. The 

 difference will not usually be of extreme im- 

 portance. A still better plan, when the ob- 

 server makes and grades a very large number 

 of similar observations, is to construct one's 

 own grade distribution curve (corresponding 

 to Fig. 1) from the tabulation of these grad- 

 ings, and from it to prepare, as above ex- 

 plained, a translation table suited exactly to 

 one's own peculiar grading characteristics. 



Summarizing this method of assigning 

 weights to original observations: 



1. First grade the observations on a scale 

 of 100 as you would students, averaging to- 

 gether the various factors that may affect 

 their reliability. In doing this, endeavor to 

 maintain the same mental attitude toward the 

 experiments as you would toward the work of 

 a class of students. 



2. Then consult the above translation table 

 (or one of your own making) for the proper 

 weights to be assigned. 



LeEoy D. Weld 

 CoE College, 

 Cedar Eapids, Iowa 



THE AMERICAN CHEMICAL SOCIETY. 

 Ill 



division op indijstrlal chemists and chemical 



engineers 



H. S. Miner, Chairman 



H. E. Howe, Secretary 



Incendiaries used in modern warfare: Capt. A. 

 B. Bay. 



Gas masTcs in the industries: A. C. Pieldner. 

 The Bureau of Mines is cooperaiting with the in- 

 dustries in the development of suitable modifica- 

 tions of the Army gas mask for industrial use. In 

 the nine months that have elapsed since the signing 

 of the armistice, the gas mask has made rapid 

 progress in finding a wide application in protect- 

 ing workmen from poisonous and irritating gases 

 given off in various chemical operations; as for 

 example, chlorine, phosgene, sulphur dioxide, oxides 

 of nitrogen, hydrochloric acid, sulphur chloride 

 and many organic vapors as carbon disulphide, 

 benzol, carbon tetrachloride, aniline, chloroform, 

 formaldehyde, etc. Eire departments have pur- 

 chased many Army masks for use as smoke pro- 

 tectors. However, they must be used with caution 

 around fires, as they given no protection from 

 carbon monoxide, which may be present in smoky 

 atmospheres. The Army gas mask, when fitted 

 with special canister containing ammonia absorb- 

 ents, has met with great success for use around 

 refrigerating plants. On the whole, the gas mask 

 is rapidly finding its proper place in the indus- 

 tries. It has not met all the requirements ex- 

 pected, especially in such cases where the work- 

 men must wear it for long periods of time. Ex- 

 perience has shown that they simply will not wear 

 a mask continuously if they can possibly get along 

 without it, but for short periods and in emergen- 

 cies, it has proved very useful. The possibilities 

 of the gas mask principle are now pretty generally 

 understood, and much improvement in design may 

 be expected within the next year. 



Tlie physical character of hydrous ferric oxide: 

 Harry B. Weiser. 



Modern commercial explosives: E. H. Hill. 

 Paper disputes the war-developed, current idea 



