THURSDAY, APRIL 17, 1919. 



GYROSCOPICS. 



A Treatise on Gyrostatics and Rotational Motion. 



Theory and Applications. By Prof. Andrew 



Gray. Pp. xx + 530. (London : Macmillan and 



Co., Ltd., 1918.) Price 425. net. 

 •T^HE exhibition at the International Mathe- 

 -*- matical Congress at Cambridge in 1912, 

 although unnoticed in the official record of the 

 Proceedings, was attractive as a collection of 

 scientific books on view of all the chief publishers 

 in the world, and of apparatus designed for use in 

 mathematical instruction, including a very com- 

 plete assortment of calculating machines of all 

 kinds. 



But the foreign visitor was delighted chiefly to 

 see and handle the gyrostats and apparatus, and 

 so to clear up much of the obscurity in the mere 

 description and diagrams of the "Treatise on 

 Natural Philosophy " of Thomson and Tait. 



The apparatus was designed, and explained, 

 and shown at work in the skilful hands of Dr. 

 James Gray, son of our author, engaged since in 

 the development of the warlike applications ; and 

 we are promised a sequel devoted to this side of 

 the subject of gyrostatics as soon as the seal of 

 secrecy has been removed with the advent of 

 peace. 



Mention and description can then be made, too, 

 of the peaceful applications of gyroscopic prin- 

 ciples, such as to the design of the centrifuges 

 employed for centrifugal and whirling operations 

 in chemical and laundry work, to drain off the 

 moisture in a saturated substance swiftly and 

 with no internal disturbance. These were de- 

 scribed in Engineering for February 7 last, where 

 each centrifuge must be treated as a great 

 spinning-top, upright as if asleep, requiring the 

 upper end to be quite free in precession, and so 

 actuated from the lower end of the axle, in this 

 case by a Pelton wheel. 



The gyro-compass is held over to the sequel, as 

 involving the operation of secret processes ; with- 

 out it the navigation of a submarine could not have 

 been possible. But a full description is given in 

 chap. viii. of Schlick's sea gyroscope, with the 

 theory designed to ensure a dry ship and easy 

 roller in all weather. 



Prof. Gray has succeeded, in the chair of natural 

 philosophy at Glasgow University, to the gyrostatic 

 apparatus of Lord Kelvin, his predecessor, and has 

 added important developments of his own inven- 

 tion. As show^n in the diagrams, these are of 

 elaborate construction, and demand the aid of 

 electric motive power to impart and maintain the 

 high rate of revolutions required, and so will not 

 be allowed far from the lecture-desk. 



But Maxwell's opinion must be maintained that 

 the real instruction of the student is derived from 

 the crude apparatus made by his own hands, and 

 that he learns most from his own failures. 



So we venture to suggest to Prof. Gray the en- 

 NO. 2581, VOL. 103] 



NATURE 



121 



couragement of his students in the use of such 

 simple apparatus as that in his Fig. 30(b) on 

 p. 128, where a bicycle wheel is shown as a cheap, 

 efficient top, spun by hand, and no string or elec- 

 tric motor is required. If the ordinary 28-in. wheel 

 is not considered large enough, it will cost little 

 more to order one of double or three-fold diameter, 

 as the delicate part of the hub and ball-bearings 

 can serve for all, and is bought cheap when manu- 

 factured in large quantities These can be handled 

 and thrown about, and brandished, and so provide 

 the muscular sensations on a large scale of gyro- 

 scopic domination. Any inventor's idea can be 

 tested at once and an advantage followed up. 



If the point of a top is free to wander about on 

 the floor, either as a sharp tip or a rounded ball, 

 the dynamical treatment is intractable in the 

 present state of mathematical analysis. 



The point must be kept still, and we avoid the 

 hideous unreality of the "perfectly rough " of the 

 text-book jargon by placing it, as in Fig. 30(a), 

 in a small cup recess, the wheel spinning freely 

 about the ball-bearings of the hub fixed on the 

 stalk. 



The top must then have uniaxial symmetry if the 

 motion is to be expressible by the elliptic func- 

 tion, as explained in chap. xii. ; and these functions 

 appear created expressly to speak the language of 

 such gyroscopic motion. 



In the old Cambridge mathematical tradition, 

 praised by Todhunter, it was considered of no in- 

 tellectual merit to have seen and worked an experi- 

 ment in Natural Philosophy and not to have 

 grasped the idea by mere thinking. 



Maxwell strove hard to destroy this tradition, 

 and pointed out the superiority at Glasgow of Sir 

 William Thomson's stimulating treatment of dyna- 

 mics with experiments. Maxwell was given a 

 chance of working out his ideas by the erection of 

 the Cavendish Laboratory for his benefit, gift of 

 the Chancellor, the Duke of Devonshire. But as 

 Maxwell's inaugural lecture was delivered to bare 

 walls, the Chancellor desired to make his gift 

 complete by presenting an appropriate collection 

 of apparatus. Such an order could not be given 

 out at once in those days, and the demands ex- 

 tended over a few years, during which some busy- 

 bodies, self-styled business men, were always 

 worrying Maxwell to make his final demand and 

 declare the Cavendish Laboratory complete ; and 

 as Maxwell was then approaching his fatal illness 

 he was too weak to protest, leaving his successor, 

 Lord Rayleigh, the inheritance of a large establish- 

 ment with no endowment for upkeep and progress. 



The tradition there of research has been chiefly 

 electrical, so that the interests of dynamics have 

 not been studied equally, and, to judge from the 

 ordinary text-books in use, the old Victorian tra- 

 dition still survives, copied from one to the other, 

 and not looking up from the page at the great 

 developments taking place around, a great con- 

 trast to Prof. Gray's treatise before us. 



The elliptic function solution is restricted to the 

 top of uniaxial symmetry. If the top is taken to 

 be a body of any shape, as may be imitated with 



H 



