﻿162 Notices respecting New Books. 



A kite or balloon picture being out of the question, on 

 account of the long exposure required, the camera was carried 

 to the top of the monument' located at the centre of Mount 

 Vernon Place, lashed to the underside of a twelve-foot piece 

 of timber, and run out over the edge of the parapet, which 

 surrounds the top of the cylindrical shaft. The view obtained 

 in this way is shown in fig. 5, a portion of the city being of 

 course hidden by the monument. 



An improved form of fish- eye camera was subsequently 

 constructed. The box was made of sheet-brass, and measured 

 4x5x2 inches (inside measurement). The plate was 

 inserted through a slot provided with a hinged metal cover 

 and rubber washer, and the optical part made by cementing 

 a piece of tinfoil, perforated with a needle-hole, between two 

 pieces of plate-glass, with Canada balsam. The plates were 

 then cemented over a circular hole 2 inches in diameter, cut 

 in the top of the metal box. This arrangement was so com- 

 pact that it could be carried in the coat-pocket, and was 

 absolutely water-tight. It seems quite possible that the peculiar 

 type of refraction described in the present paper, which makes 

 a working angle of 180° possible, may be made use of in 

 certain cases. Since the device will photograph the entire 

 sky, a sunshine recorder could be made on this principle, 

 which would require no adjustment for latitude or month. 

 While the views used for the illustration of this paper savour 

 somewhat of the " freak " pictures of the magazines, it is 

 believed that the fact that they illustrate how one half of the 

 world appears to " the other half " is sufficient excuse for 

 their publication. 



Baltimore, June 1906. 



XXIV. Notices respecting New Books. 



Physical Optics. By Eobeet W. Wood, Professor of Experi- 

 mental Physics in the Johns Hopkins University. New York : 

 The Macm'illan Co. 1905. 



TF we have not been so forward with the review of this book as 

 -*- we might have been, it is in part to be ascribed to the merits 

 of the book itself. We have bad, midst the pressure of other work, 

 to read a great deal more than the reviewer is wont to read before 

 committing his opinions to paper. 



Professor Wood's ' Physical Optics ' is at once a teaching book of 

 value, a compendium of practical details for laboratory work, and 

 a brilliant exposition of recent problems of Physical Optics. We 



