June 3, 1920] 



NATURE 



427 



the Saskatchewan River and the Arctic " Barren 

 Grounds," and his collection of birds from the area 

 drained by the Churchill River was the first to be 

 made frorri that remote region. Of this collection 

 a list is given at the end of the book, and birds 

 predominate throughout the pages of what is 

 really a naturalist's journal — unvarnished, graphic, 

 and with a strong personal note. A chapter is 

 given to the rare sandhill crane, which he saw 

 and heard and stalked. He found the nest and 

 saw the eggs through the field-glass, but, having 

 waited overnight in the hope of the parents return- 



ward migration, so it is leisurely ; moreover, many 

 of the does are with young. The southward 

 movement of great herds in the fall is largely con- 

 ditioned by the absence of trees, for an icy crust, 

 difficult to break, forms over the snow. "As the 

 thermometer drops in the Far North and food 

 and shelter become diflficult to find, the animals 

 will band together and grow restive, and pause 

 from time to time to sniff the wind from the south 

 with question on their countenance. And one day,' 

 with proud heads up and anxious eyes, they will 

 commence their long travel throuq-h sheltering 



Fig. 3.— Caribou travelling in typical Indian file. From "Wild Life in Canada.' 



ing, he was baulked in the end, for the nest was 

 empty in the morning. 



A fine picture is given of Reindeer Lake, a vast 

 sheet of water stretching 140 miles north and 

 south, and 40 miles across at its widest. Its 

 shores form the favoured winter-haunt of the 

 barren-ground caribou [Rangifer arcticus), which 

 digs through the snow to get at the white moss 

 and marsh grass. Early in the year the does and 

 yearling fawns begin to move northward, and the 

 bucks follow later. 



There is no weather-change urging the north- 



forests where snows are soft and food is plentiful 

 beneath its yielding surface." 



The picture that the author gives of the caribou 

 is a fine piece of work. Another chapter deals 

 with the admirable sled-dogs, which will gamely 

 do their best, for two or three days on end, in 

 bitter weather and without food, to save an 

 anxious situation. Very good reading, too, is 

 Capt. Buchanan's appreciation of the Cree and 

 Chipewyan Indians, "quaintly friendly and 

 unselfish in their hospitality," "resourceful, mag- 

 nificent fellow-travellers on the trail." 



Tidal Power. 



THE idea of utilising the rise and fall of the 

 tides for power purposes has long been a 

 favourite one. Up to the present, however, no 

 power development of this kind, of any 

 appreciable size, has been carried out. The com- 

 paratively recent arousing of interest in water- 

 power development in general, and the great 

 advance in the cost of fuel, have been accompanied. 

 by a corresponding interest in tidal-power 

 schemes, and their commercial possibility is at 

 the moment the subject of serious investigation 

 in this country and in France. 



The power which may be developed from a 

 tidal basin of given area depends on the square 

 of the tidal range, and since the cost per horse- 

 power of the necessary turbines and generating 

 machinery increases rapidly as the working head 

 is diminished, the cost per horse-power of a tidal- 

 power installation, other things being equal, will 

 NO. 2640, VOL. 105] 



be smallest where the tidal range is greatest. It 

 is for this reason that the western, and especially 

 the south-western, coasts of Great Britain, and 

 the western coast of France, are particularly well 

 adapted for such developments, since the tidal 

 range here is greater than in any other part of 

 the world, with the possible exception of the Bay 

 of Fundy, Hudson's Bay, and Port Gallelos, in 

 Patagonia. 



In Great Britain the highest tides are found 

 in the estuary of the Severn, the mean range of 

 the spring tides at Chepstow being 42 ft., and 

 of the neap tides 21 ft. In France the maximum 

 range occurs at St. Malo, where it amounts to 

 425 ft. at spring tides, and about 18 ft. at neap 

 tides. The tidal range in the Dee is 26 ft. at 

 springs, and 12 ft. at neaps, while the mean 

 range of spring tides around the coast of Great 

 Britain is 164 ft., and of neap tides 8'6 ft. 



