March 18, 1921] 



SCIENCE 



267 



©ation. The results so far oTjtained indicate that, 

 prortded a sufficient amount of kieselg^r is used 

 to afford the minimum adsorbing surface required 

 for the colloids present, there is little, if any, dif- 

 ference in clarifying eflSeiency when equal weights 

 are used, even though the various kieselguhrs may 

 differ considerably in physical properties. The 

 dialysis experiments further proved, as has been 

 indicated by the work of previous investigators, 

 that heating and filtration with kieselguhr remove 

 all colloids of such a degree of dispersion as to 

 give a turbidity visible to the eye. Using activs 

 decolorizing carbon after preliminary treatment 

 of the juice with kieselguhr, it was found that 

 coUoids of such dimensions as to be invisible to 

 the eye were thereby removed. 



Determination of the density of molasses: W. B. 

 Newkikk. The picnometer suggested permits a 

 greater accuracy in the determination of the den- 

 sity of molasses than has been possible hereto- 

 ■ fore. It is essential for commercial reasons that 

 an accurate method of determining the density be 

 used. The interfering obstacles in the determi- 

 nation of den^ties of molasses are due to the 

 high visSosity, included gases and dissolved gases. 

 The picnometer suggested is adaptable in the 

 presence of these difficulties. It consists of a 

 bottle fitted with an enlargement at the top 

 ground optically flat and closed off by another 

 optical flat. An expansion chamber is ground 

 on to the bottle to permat the expansion of the 

 included gas to permit of its easy removal and is 

 fitted with a vacuum coimecition and stop cock in 

 order to put the contents of the bottle under 

 greatly reduced pressure and maintaining the 

 same for a considerable length of time, without 

 the loss of moisture. The evaporation is negli- 

 gible. The change in temperature of the picnom- 

 eter after closing is reduced by very thick walls 

 over the neck of the flask. This reducing tem- 

 perature changes on handling. Two methods of 

 deaerating were studied — the application of heat 

 to reduce its viscosity and the application of air 

 to expand the entrained gas. The heating causes 

 considerable decomposition and has a deleterious 

 effect in the determination of the density. The 

 vacuum method removes entrained gas and does 

 not have the bad features of heating or dilution. 

 The accidental errors are shown to be very small 

 and the total error in any one direction is shown 

 to be within .1 of 1° Brix, and the majority of 

 determinations can be made within a few hun- 

 dredths of 1° Brix. Densities with this apparatus 



can be determined with reasonable facility and 

 with considerably more accuracy than the sample 

 of molasses can be obtained. 

 I Chaeles L. Parsons, 



Secretary 



ASSOCIATION OF AMERICAN 

 GEOGRAPHERS 



The annual meeting of the Association of Amer- 

 ican Greographers was held with the department of 

 geography of the University of Chicago during 

 Convocation "Week. Five sessions were held at 

 which forty-one papers were read, nine by title. 



Especial interest centered in the joint meeting 

 with the Ecological Society of America and the 

 session devoted to invited papers on industrial 

 geography. The papers given at the joint meet- 

 ing were as follows: 



Experimental animal climatology : V. E. Shelpoed. 

 Geography in zoological museums: A. G. Euthvbn. 

 The relation of plants to new habitats: D. T. Mac- 



DODGALL. 



Ecology and geographic boundaries: H. C. Cowles. 



Owing to the necessary absence of President 

 Gregory, because of an emergency telegram, his 

 presidential address on "Geographic basis of the 

 political problems of the Pacific" was omitted. 

 The following papers on Industrial Geography 

 were given during the afternoon session of the 

 same day. 

 The significance of vegetable oils in the economic 



development of the tropics: V. C. Pinch. 

 Geographical influences in marketing; illustrated 



by the meat industry: Guy C. Smith. 

 Geographic factors in dairy farming in southern 



New England: Eichaed E. Dodge. 



The papers presented at the remaining sessions 

 were as follows: 

 Mainfall maps of Latin America: Eugene Van 



Cleef. 

 The trade winds and anti-trades of Porto Mico: 



Oliver L. Passig. 

 Progress in organization of the CUmatological 



Service of the West Indies: Oliver L. Passig. 

 Bise in temperature on mountain summits earlier 



than on valley floors : H. J. Cox. 

 Cold surf with off shore winds: Charles P. 



Brooks. 

 Vertical gradients of evaporation and soil mois- 

 ture in desert and coastal mountains: Porrest 



Sheeve. 

 Stream and ocean terraces in relation to recent 



earth movements : R. S. Holwat. 



