270 Mr. W. H. Preece. On a New Standard of 



Observations, &c. (continued). 



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The Registrar- General for New Zealand. 

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 XVIII. Lief. 5 nnd Titelheft. 4to. Jahrg. XIX. 4to. Zurich. 



The Institution. 



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Asclepiad. A Book of Original Research and Observation. By 

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Dr. Richardson, F.R.S. 

 Astr onomische Xachrichten. Band CVI. 4to. Kiel 1883. 



The Editor. 



Fortschritte der Physik. Jahrg. XXXVI. 8vo. Berlin 1882-83. 



The Berliner Physikalischer Gesellschaft, 

 Mittheilungen ans der Zoologischen Station zn Xeapel. Band IV. 

 Heft 4. 8vo. Leipzig 1883. The Zoological Station. 



Attfield (John), F.R.S. Chemistry: General, Medical, and Pharma- 

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Baltet (Charles) Action du Froid sur les Vegetaux pendant l'Hiver. 

 1879-80. 8vo. Paris 1882. Societe d' Agriculture de France. 



Lefroy (Sir J. £L), F.R.S. Diary of a Magnetic Survey of a Portion 

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Sewell (Robert) A Sketch of the Dynasties of Southern India. 4to. 

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The Author. 



" On a New Standard of Illumination and the Measurement of 

 Light." By William Henry Preece, F.R.S. Received 

 and read June 21, 1883. 



1. The present position of photometry as practically applied to 

 electric lighting is by no means in a satisfactory condition. Mathe- 

 matical accuracy in the measurement of the intensity of the light 

 emitted by a given source is unobtainable owing to the numerous 

 disturbing influences of quality and quantity which render impossible 

 any graduated scale of light. An absolute standard of light has not 

 yet been obtained. I have long felt that to meet the case of electric 



