Bragg's interest in physics developed, particularly in the field of electromagnetism. In 1895, he was visited by Ernest Rutherford, en route from New Zealand to Cambridge; this was the commencement of a lifelong friendship. Bragg had a keen interest in the new discovery of X-rays by Wilhelm Röntgen. On 29 May 1896 at Adelaide, Bragg demonstrated before a meeting of local doctors the application of "X-rays to reveal structures that were otherwise invisible". Samuel Barbour, senior chemist of F. H. Faulding & Co., an Adelaide pharmaceutical manufacturer, supplied the necessary apparatus in the form of a Crookes tube, a glass discharge tube. The tube had been obtained at Leeds, England, where Barbour visited the firm of Reynolds and Branson, a manufacturer of photographic and laboratory equipment. Barbour returned to Adelaide in April 1896. Barbour had conducted his own experiments shortly after return to Australia, but results were limited due to limited battery power. At the University, the tube was attached to an induction coil and a battery borrowed from Sir Charles Todd, Bragg's father-in-law. The induction coil was utilized to produce the electric spark necessary for Bragg and Barbour to "generate short bursts of X-rays". The audience was favorably impressed. Bragg availed himself as a test subject, in the manner of Röntgen and allowed an X-ray photograph to be taken of his hand. The image of the fingers in his hand revealed "an old injury to one of his fingers sustained when using the turnip chopping machine on his father's farm in Cumbria".