June 15, 1900.] 



SCIENCE. 



951 



exposure is longer, and a negative if the espo- 

 sure is shorter. The bath used in the above 

 illustration must be weak and cool. 



If a fresh plate is exposed in our camera with 

 full opening to a brilliantly lighted street scene 

 for one minute, it will develop as a positive in 

 that same bath. This time can be somewhat 

 reduced, but the least time needed has not yet 

 been determined. It is evident that part of 

 this minute is used in producing a zero plate. 

 It is furthermore clear that different parts of 

 the plate will arrive at the zero condition at 

 dififerent times. The exposure may be arrested 

 at a time when the strongly lighted white back- 

 ground of a sign-board will develop white as a 

 positive, and when the black letters will also 

 show white as a negative. 



It has been found that when a plate is uni- 

 formly exposed over its whole surface to the 

 extent that nothing would have developed had 

 it been covered by a stencil, this plate may 

 then be placed in a camera and exposed in the 

 ordinary way, and a perfect positive will de- 

 velop in the bath to which it has been adapted. 

 This preliminary spoiling of the plate for de- 

 veloping a negative is a very advantageous 

 preparation for taking a positive. It shortens 

 the time of exposure, and ensures that a posi- 

 tive shall be obtained over all parts of the plate. 

 It is not yet known how short the camera ex- 

 posures may be made, but the present indica- 

 tions are that they will be as short as those now 

 made in the taking of negative pictures. 



It is currently believed by photographers that 

 in a positive plate the object has ' printed its 

 picture ' upon the plate. This is an entire mis- 

 conception of the process. It is true that in 

 an exposure of long duration an image shows 

 on the plate before it is placed in the bath. 

 But this image is blackest where the light has 

 acted most. It is a negative. This picture 

 disappears in the developing bath when il- 

 luminated. The plate becomes perfectly 

 clear. The positive picture then develops, 

 exactly as a negative would under ordinary 

 conditions. 



Mr. J. B. S. Norton presented some notes on 

 the flora of the southwestern United States. 

 Maps were shown indicating the parts of this 

 region and others not well represented in her- 



baria, as compared with other sections of the 

 country. Among other interesting features of 

 the Southwest was mentioned the production 

 of many different forms or closely related spe- 

 cies in the isolated mountains surrounded by 

 deserts. This was compared with insular con- 

 ditions and illustrated by the mountain forms 

 of Euphorbia. Specimens of some new species 

 from southwest Missouri were also shown. 



Two persons were elected active members of 

 the Academy. 



William Teelease, 

 Recording Secretary. 



NEW TOEK ACADEMY OF SCIENCES. 

 SECTION OF BIOLOGY. 



At the regular meeting of May 14, 1900, 

 Professor F. S. Lee, presiding, the following 

 papers were presented : 



' Some Chemical Notes on the Composition 

 of the Cocoanut,' by J. E. Kirkwood and Wm. 

 J. Gies. 



The authors have carried on qualitative work 

 on the ungerminated nut, preparatory to a study 

 of the digestive processes during germination. 

 The chief constituents are cellulose and fat. 

 Some soluble carbohydrate is present, beside 

 globulin and proteose, but no albumen or pep- 

 ton. Only amylolytic ferments have so far 

 been found. The milk of the nut is normally 

 acid, probably due to acid phosphate. It con- 

 tains an earthy phosphate, reduces Fehliug's 

 solution, sours on standing, and acquires much 

 the odor and physical appearance of soured 

 cow's milk. It shows only small quantities of 

 proteid and fat. 



The meat of the average nut contains from 

 two to three grains of globulin, which may be 

 obtained in crystalline form. The authors have 

 made three preparations by the usual methods. 

 The nitrogen averages for these were ll.Qlfo, 

 17.81 /o, 17.68/0. The ash for the same, 0.13/c, 

 0.41^, 1.05fo. From the meat of twelve nuts 

 it was possible to separate a little more than 

 three grains of proteose by the usual method. 

 The average of three closely agreeing determi- 

 nations of nitrogen was 18.57^; of the ash it 

 was 1.71 fo . The quantitative relationships of 

 these and other constituents will be subjects 

 of combined investigation. 



