BRIEF NOTES. 



2ST 



BEIEF NOTES 



Waste of Power at Niagara. — Dr. Siemens, 

 in an address to the London Iron and Steel Insti- 

 tute, referred to several instances of available 

 power being lost, owing to the inadequacy of our 

 present means of utilizing it. The falls of Nia- 

 gara are, he said, a familiar example of this. 

 The amount of water passing over this fall has 

 been estimated at 100,000,000 tons per hour, and 

 its perpendicular descent may be taken at 150 

 feet, without counting the rapids, which repre- 

 sent a further fall of 150 feet. But the force 

 represented by the principal fall alone amounts 

 to ] 6,800,000 horse-power. In other words, all 

 the coal raised throughout the world would bare- 

 ly suffice to produce the amount of power that 

 continually runs to waste at this one fall. Much 

 of this power might be turned to account on the 

 spot by means of water-wheels, but the district 

 around about is devoid of mineral wealth or 

 other natural inducements for the establishment 

 of factories. Dr. Siemens then mentions plans 

 for carrying and utilizing water-power at a dis- 

 tance of one or two miles. But the problem still 

 remains, How shall power be carried to great dis- 

 tances? Dr. Siemens suggests the electrical con- 

 ductor. " Suppose," he says, " water-power to 

 be employed to give motion to a dynamo-electri- 

 cal machine, a very powerful electrical current is 

 the result. This may be carried to a great dis- 

 tance, through a large metallic conductor, and 

 there be made to impart motion to electro-mag- 

 netic engines to ignite the carbon-points of elec- 

 tric lamps, or to effect the separation of metals 

 from their combinations. A copper rod of three 

 inches in diameter would be capable of transmit- 

 ting 1,000 horse-power a distance of say thirty 

 miles, an amount sufficient to supply 225,000 can- 

 dle-power, which would suffice to illuminate a 

 moderately-sized town." 



Do Birds hibernate? — In the course of a re- 

 view of a work on " The Migration of Birds," a 

 writer in Nature ridiculed the idea of birds 

 "hibernating," and asserted that there is abso- 

 lutely no valid evidence in favor of the supposi- 

 tion that birds ever lie dormant. But now comes 

 a communication to the same journal from the 

 Duke of Argyll, inclosing a letter fiom Sir John 

 McNeill, who very distinctly upholds the contrary 

 opinion, namely, that birds do hibernate. Hav- 

 ing, in company with Sir Henry Rawlinson, during 



a very severe frost, visited a place called Kenara- 

 gird, near the Persian capital, for the purpose of 

 duck-shooting, he came to a spot where, in the 

 bank of a stream, there had been a small land- 

 slip. On the ground between the detached por- 

 tion and the perpendicular face from which it 

 had broken off, he saw twenty or thirty swallows, 

 all alive, but dormant. On the perpendicular 

 face of the bank was visible a vast number of 

 holes about the size of rat-holes, and in them were 

 swallows in the dormant state, many of which Sir 

 John pulled out. Each hole contained several 

 swallows, all lying with their heads inward, each 

 head touching the tail of the bird before it. 

 How far these holes penetrated into the bank, 

 or what number of swallows each contained, he 

 did not ascertain ; but it is plain that the original 

 entrance to these dormitories must have been in 

 the external face of the portion that had slipped, 

 which, in the middle, was from ten to twelve feet 

 thick. The holes in the undisturbed portion 

 may have been of equal or greater length ; and 

 if so the number of swallows hibernating here 

 must have amounted to many hundreds. 



Sir William Grove on the Radiometer. — Sir 

 William Grove, in two communications to the 

 Philosophical Club, abstracts of which have ap- 

 peared in Nature, describes some experiments 

 made by him with a modification of Mr. Crookes's 

 radiometer, and the result of which appears to 

 show that all the effects observed in this instru- 

 ment are due to residual air. In the modified 

 radiometer used in these experiments the four 

 aluminium vanes, each blackened on one side, 

 had metallic arms, and a metal point at their 

 crossing that rested in a metal cup. The latter 

 was united to a platinum wire passing through 

 a glass tube and fused into it, the end of the wire 

 protruding. Finally, the tube was fused inside 

 the stem of the radiometer-bulb, the end of the 

 platinum wire being exposed. Mr. Crookes pro- 

 nounced the vacuum to be as perfect as in radi- 

 ometers generally. With this instrument the fol- 

 lowing results were obtained : 1. With the light 

 of a lucif'er-match, or of one or two candles, the 

 vanes invariably turned in the opposite way to 

 the normal, the polished surface being repelled ; 

 with dark heat they turned in the normal way. 

 2. On electrizing the protruding platinum wire 

 with a rubbed rod of glass or sealing-wax, the 



