390 



SCIENCE 



[N. S. Vol,. XXVII. No. 688 



for all wave-lengths greater than .4 jj, so that 

 the second order ultra-violet might not over- 

 lap the continuous spectrum. The spectrum 

 -of the Nernst glower was too weak to affect 

 the plates at .385 /j. in the first order, and 

 could not therefore have produced any effect 

 below .650/4 by the overlapping of the second 

 order. A 75-second exposure was usually 

 given to the spark, then the screen was re- 

 moved and a one-minute exposure given to 

 the spectrum of the Nernst glower. The 

 ■spark terminals were made very broad and 

 chisel-shaped and their edges were placed 

 "parallel to the slit, a considerable length 

 (about a centimeter), of which was thus 

 illuminated. A large Ley den jar was con- 

 nected across the spark gap. 



An ingenious form of cell for holding the 

 -absorbing liquids is described in full. By 

 means of it a wedge-shaped film of liquid was 

 confined between qtiartz plates which could 

 be set at any desired angle to each other 

 and at any distance apart up to 6 mm. 

 "When properly placed before the slit the light 

 coming to each successive point of the slit 

 came through successively increasing thick- 

 nesses of the dye. Three exposures were 

 usually made on each plate, their edges nearly 

 in contact and the angle of the wedge and its 

 position at each exposure was such that the 

 three photographic strips showed, from the 

 top of the first to the bottom of the last, the 

 ■effect of a continuously increasing thickness 

 of the absorbing film. The thickness at one 

 ■edge was zero and at the other usually about 

 .25 mm., although the thickness at the thicker 

 «dge varied over a considerable range. 



The authors have anticipated the chief 

 criticisms which might have been advanced 

 against the book. In stating their " chief 

 object " they disclaim any intention to at- 

 tempt quantitative measurements or to make 

 an exhaustive study of all known dyes. They 

 bave certainly investigated " a reasonably 

 large number of compounds." Their state- 

 ment that " only aqueous solutions of the 

 aniline dyes have been investigated up to the 

 present time " leads us to hope that the in- 

 vestigation -will be continued both for other 

 solvents and for other dyes, including some 



of the very important new photographic dyes 

 which are not in their present list. 



No attempt has been made to give to a high 

 degTce of exactness the positions of the ab- 

 sorption bands, and it is doubtful if either 

 this or the relative strengths of the. absorp- 

 tion bands could have been found satis- 

 factorily with the commercial plates used. 

 And it is perhaps because no attempt in this 

 direction was intended that no data are given 

 as to time of development, temperature of 

 developing bath, etc. — nor are we told whether 

 or not any attempt was made to secure uni- 

 formity in these respects. 



The authors give ample warning that the 

 photographic minimum in the Seed plates 

 used may produce apparent absorption in the 

 green. Without doubt there is much of in- 

 terest in the red of many of these dyes, and 

 it is to be regretted that the authors did not 

 make use of some of the modern methods of 

 plate bathing, or even of some of the later 

 plates now obtainable commercially, both to 

 secure a more uniform photographic sensi- 

 tiveness throughout the spectrum, and to ex- 

 tend the observations into the red. As they 

 point out, however, the slope of the limiting 

 line at the red end of their plates indicates 

 whether or not an absorption band is present 

 in that region. 



The book is very well printed and the 

 plates seem to be excellent, although they do 

 not seem to show all that may be seen on 

 the original negatives, as is evidenced by a 

 comparison of the tabulated data of some of 

 the figures with the figures themselves, e. g., 

 in the case of potassium permanganate. Fig. 

 75, we are told that the negative shows seven 

 absorption bands in and near the green. Only 

 five of the seven can be detected in Fig. 

 74. The absence of typographical errors is 

 noticeable. TJnder Fig. 99, however, we are 

 referred to page 169, instead of, evidently, 

 page 59. Heney G. Gale 



Ryekson Phtsical Labobatory 



SOCIETIES AND ACADEMIES 

 THE OREGON STATE ACADEMY OF SCIENCES 



The third annual meeting of the Oregon 

 State Academy of Sciences was held at the 



