8 1 1 ALi )A N K Gee — Henry / \ llde 



The result of his many tests made with a view to the possibilities 

 of avaation showed that the solution of the problem was not to be 

 found in the discharge of gases through orihces. He then turned 

 his attention to screw propellers, and used vanes from i to 4 feet 

 in diameter, driven at velocities up to 2,000 revolutions per 

 minute ; but the results were not sufficiently encouraging to him. 

 He remarked: "Although my experimental investigations on 

 the possibility of aerial locomotion have so far been of a negative 

 character, the confidence I have in the ultimate solution of the 

 problem still remains unshaken." 



Magnetic Researches. 



On the e.xpiration of the patents relating to the dynamo in 1884. 

 Dr. Wilde retired from business. He was then fifty-one years of 

 age, and vigorous; and he decided to devote his time to scientific 

 research. During twelve years (1885-1897) his experimental work 

 chiefly related to magnetism. 



He was a great student of the works of the early investigators 

 in the subject of terrestrial magnetism, and was especially 

 attracted to the theory of Halley, the astronomer and contem- 

 porary of Newton, that the variation of the magnetic compass 

 could be explained by the rotation within the earth of magnetic 

 matter. This led him to design an apparatus that he called a 

 " Magnetarium." It consisted of two concentric spheres, as shown 

 in Fig. 4 (one half of the outer sphere being removed to show 

 the inner). The inner sphere, which is 16 ins. in diameter, is 

 wound over its whole surface with insulated copper wire. The 

 outer sphere, two inches greater in diameter than the inner one, 

 has its inner surface covered with iron wire gauze, over which is 

 wound a magnetising coil. The spheres were mounted on axles 

 as shown, and they could be revolved at difi"erent rates of speed 

 by turning the handle, which operated gearing. The axles 

 are supported on a semi-circular brass meridian mounted between 

 rollers fixed to a vertical support. All observations of dip and 

 variation were made by bringing the station under test beneath 

 an upper small circular table on which a dip needle or declina- 

 tion compass can be placed. The magnetising coils were con- 

 nected in parallel to a small magneto, and by variable resistances 

 the currents in the two circuits could be adjusted. In order to 

 represent more accurately the distribution of the earth's mag- 

 netism, it was found necessary to cover the spaces representing 

 the oceans with thin sheets of iron and to fix the inner globe at 

 an inclination of 23J degrees to the axis of the terrestrial sphere. 

 The train of wheels was so arranged that the internal sphere lost 

 12° for each revolution of the terrestrial globe, and this was 

 taken as equivalent to 32 years. It was found possible by this 

 magnetarium to represent fairly Avell the distribution of mag- 

 netism in time and place. 



