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DULAU 81 Co., Ltd., 



34-36, MARGARET STREET, CAVENDISH SQUARE, LONDON, W. 1, 



Have always on hand a very extensive stock of works on the Natural 

 and Physical Sciences — both Secondhand and New. 



CATALOGUES SENT FREE ON APPLICATION. 



Libraries or small Collections of Books Purchased. Distance no object. 



SCIENTIFIC BOOKS & SERIALS. 



JOHN WHELDON & Co. have the largest stock in the 



country of Books in all departments of Science and Natural 



History, also Transactions and Journals of Learned Societies, 



etc., in sets, runs, and single volumes or numbers. 



A LARGE SELECTION OF BOOKS ON ENTOMOLOGY. ANY WORK 

 QUO TED FOR. 



LIBRARIES OR SMALL PARCELS PURCHASED. 



SPECIAL CATALOGUES: Entomological, Botanical, War Economy (Agriculture. 

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38, GREAT QUEEN STREET, KINGSWAY, LONDON, W.C. 2. 



Teleohone : GERRARD 1412. 



Messrs. 



W. HEFFER & SONS, Ltd., 



Booksellers , 



CAMBRIDGE, ENGLAND, 



Have a very highly organised department for the 

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Now ready : Catalogue of Scientific Books and Publi- 

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Telegrams and Cables : " Heffer, Cambridge." 



