Geology and Mineralogy. 79 



street was strongly lighted, and the plate was converted into a 

 zero condition, and the positive was then produced, during the 

 single minute and while in the camera. 



It is also found that the camera exposure may be shortened, by 

 fogging the plate in open lamp-light before it is put into the 

 camera. If the plate is to be developed within 20 cm. from a 

 sixteen-candle lamp, these fast plates will be put into a zero con- 

 dition by holding them for 90 seconds at a distance of one meter 

 from the lamp. When exposed in the camera such a plate yields 

 a perfect positive picture. If traces of fogging appear, the plate 

 should be moved nearer the lamp. The precise conditions which 

 yield the best results have not yet been determined, nor is it yet 

 known how short the exposure may be made. Some of the plates 

 turn out badly until experience has been gained. 



It is evident that if a similar change can be produced in the 

 operation of printing, so that a positive print may be obtained 

 from a positive plate, the dark-room may perhaps be dispensed 

 with for purposes of developing. 



In some cases the most sensitive plates have been exposed for 

 from three to four hours to brilliantly lighted street scenes, with 

 the diaphragm fully open. There is not the least trouble in devel- 

 oping such plates, as positives, in a strongly lighted room. In 

 general, the greater the exposure, the darker the developing room 

 must be in order to get a zero or a negative result. 



Large pin-hole images of the sun may be developed in this way, 

 and there appear to be many ways in which the process may 

 yield good results. One of the incidental features of value is that 

 a little of what photographers most fear does not interfere with 

 the results. 



II. Geology and Mineralogy. 



1. A Monograph of Christmas Island {Indian Ocean): Phys- 

 ical Features and Geology ; by Charles W. Andrews. With 

 descriptions of the Fauna and Flora by numerous contributors. 

 Pages x, 337 ; plates xxii. London, 1900 (British Museum of 

 Natural History). — The unique character of Christmas Island, in 

 its position, history, and life, gives peculiar interest to this account 

 of the results obtained from the ten months' vigorous explorations 

 made by Mr. Andrews, of the Geological Department of the 

 British Museum. 



Christmas Island has an area of 43 square miles, and rises in 

 places to a height of 1000 feet; it is covered with a dense trop- 

 ical vegetation. It is situated in the eastern part of the Indian 

 Ocean, 190 miles to the south of Java, 900 miles northwest of the 

 coast of Australia, and 550 miles east of the atolls of Cocos and 

 North Keeling. The submarine slopes about it are so steep that 

 a depth of 1000 fathoms is found within two or three miles of the 

 coast, while to the north, a depth of 3200 fathoms was found 

 (Maclear Deep), and to the south and southwest, of 3000 fathoms 



