March 22, 1918] 



SCIENCE 



293 



Canadian records is particularly striking — 

 and regrettable, in view of the apparent sig- 

 nificance of holarctic migrations in the past. 

 Omissions seem very few, considering the 

 magnitude of the work. I note the absence of 

 certain published records, e. g., Sciocoris mi- 

 crophthalmus (Palsearctic), Zehis socins 

 (Me., Mass.), and a scarcity of Maine records 

 before page 151. 



It is an especial pleasure to report the ex- 

 treme care which the author has evidently 

 taken to avoid minor errors, clerical and ty- 

 pographical. This class of mistakes, though 

 hardly susceptible of complete extermination, 

 has been reduced to an attenuated minimum, 

 contrasting most favorably with much past 

 and contemporary work. Dictyonoia tricornis 

 americana page 815, occurs in Maine, not 

 " Mo." Lethiini (properly Lethoeini) on page 

 196, and Systelloderus (properly Systello- 

 deres) on page 225, are lonesome examples of 

 misspelling, I believe. 



The typography calls for a special word of 

 praise. The choice of types and the arrange- 

 ment of the matter on the page are unex- 

 ceptionable and aid the eye greatly in making 

 quick reference, quite in contrast to the ar- 

 rangement adopted in the author's check list. 



The species are numbered in agreement 

 with the check list, additions being indicated 

 by fractions, a detail which will serve the con- 

 venience of collectors, though it conveys a 

 wrong impression regarding the number of 

 si)ecies comprised in the various groups. The 

 author gives 3,198 as the number of North 

 American species now included in the order 

 (three families excepted), a net gain of 253 

 since the check list appeared in 1916. Of 

 this total the Heteroptera number 1,629, the 

 Homoptera 1,569. 



A publication of this type must appeal to a 

 far wider circle than that of the comparatively 

 few specialists to whom it is of most im- 

 mediate and intense interest, since every 

 biologist has frequent occasion to ascertain the 

 present taxonomic status or the known dis- 

 tribution of some form with which he may be 

 concerned. Entomologists will at once per- 



ceive the value of Mr. Van Duzee's work — to 

 others it may be recommended unreservedly 

 as authoritative and reliable in the highest 

 degree. H. M. Parshley 



Smith College 



SPECIAL ARTICLES 



REPORTING MOISTURE RESULTSi 



The following quotations- is explantory of 

 the soil physicists' use of the term percentage 

 in connection with weight determinations of 

 moisture. 



Suppose a certain soil in field condition weighs 

 100 pounds to the cubic foot and carries 10 pounds 

 of water. Obviously it would contain 10 per cent, 

 of water by the wet method of calculation, or 11.1 

 per cent, of water using the absolutely dry soil 

 as the basis. ... In ordinary calculations of 

 water, . . . the percentage by dry weight is gen- 

 erally used because of its simplicity and the facil- 

 ity of expression that it affords. 



Analyses are reported by chemists both on 

 the wet and dry bases. The form in which an 

 analysis is usually stated is as follows: 



TABLE I 



Soil Analysis 



Wet Baala. Dry Basis, 

 Per Cent. Per Cent. 



Moisture 20.0 



VolatUe matter 20.0 25.0 



Ash other than silica. 10.0 12.5 



SUiea (SiO,) 50.0 62.5 



Total 100^.0^ 100.0 



It is noted that the per cent, of moisture 

 contained is not included in the dry basis 

 analysis. 



To ascertain if the practise of stating the 

 amount of water, present for every 100 parts 

 of dry material, as " per cent, of moisture on 

 the dry basis" leads to false interpretations 

 the following data was given to several chem- 

 ists and to three soil physicists: 



1 Contribution from Research Chemistry and Bac- 

 teriology Laboratories of department of horticul- 

 ture, Purdue University Agricultural Experiment 

 Station, Lafayette, Indiana. 



- ' ' Soils, their Properties and Management, ' ' 

 1915 edition, by Lyon, Fippin and Buckman. 



