INTENSITY OF SOLAR RADIATION. 



67 



All these amounts refer to the radiation falling upon one square centimetre 

 of horizontal surface. The maximum normal radiation is expressed in 

 gram-calories per sq. cm. per min. and the total radiation in gram-calories 

 per sq. cm. 



THE WORLD'S WHEAT SUPPLY— Major P. G. Craigie, 

 C.B., F.S.S., in his recent Sectional Presidential address, at the 

 Winnipeg meeting of the British Association, dealt with the future 

 of the world's wheat supply, and gave his audience the assurance 

 that there need be no gloomy forebodings as to the world's popu- 

 lation outstripping its production of wheat, as predicted by Sir 

 William Crookes and others during the last dozen years. 



SLADEN MEMORIAL EXPEDITION.— Two illustrated 

 articles, from the pen of Prof. H. H. W. Pearson, M.A., Sc.D., 

 F.L.S., of the South African College, describing his recent journey 

 in South-West Africa, in connection with the Percy Sladen 

 Memorial Expedition, appear in Nature of the 14th and 21st 

 October. In the first article Dr. Pearson explains that the expedi- 

 tion was the outcome of a study of Welwitschia. " that most 

 remarkable of West African plants." The primary object of the 

 tour was the investigation of the biology and morphology of 

 Gnetiim africanum, the only immediate relative of \Velwitschia 

 south of the Congo. The author mentions the chief flora of the 

 districts traversed during the first part of his journey, i.e., from 

 Ceres, through Namaqualand, to Keetmanshoop and Luderitzbucht, 

 and thence to Swakopmund and Welwitsch — a distance covered 

 in about 3J months. The second part of the narrative continues 

 the tour to Loanda and Mossamedes, and thence to Humpata, 

 Chibia, and Fort Ro9adas on the Cunene River. Very large Wel- 

 witschia plants were found in abundance about eight miles south 

 of Mossamedes, in the direction of Cape Negro. Dr. Pearson 

 was appointed to lecture before the Linnean Society, early in 

 November, on his botanical observations made during this ex- 

 pedition. 



