No . 135
The Trusty Servant
Win Coll and Xrays
Dr Martin Gregory ( Co Ro , 62-99 ) writes :
February 2023 saw the centenary of the death of Wilhelm Conrad Röntgen , the discoverer of Xrays . Röntgen , the Professor of Physics at the University of Würzburg , made his discovery in 1895 and was the first Nobel Laureate in Physics in 1901 . One of his first Xray photographs showed an image of the skeleton of his wife ’ s hand and led to an immediate practical application of his discovery .
Win Coll ’ s first physics don , William Bleadon Croft , came in the 1870s . Croft was very interested in electromagnetic radiation and other great advances in physics in the late nineteenth century . He was an early member of the Physical Society and a Fellow of the Royal Astronomical Society , and keen to be able to demonstrate these new discoveries
Fig . 1 : The earliest Xray photograph in the College collection , titled “ Printed from a negative made at WinColl by Messrs W B Croft and W E Abley , May 1897 .” There is a gold ring on the little finger and lead shot sprinkled across the palm . to his pupils . From the 1880s , the College employed a technician , Walter Abley , to make and service apparatus to provide Croft with a well-equipped laboratory . For example , Croft corresponded with Hertz over his discovery of Radio Waves and Abley built replicas of Hertz ’ s apparatus which are still extant and operable .
With Röntgen ’ s discovery , Croft was writing letters again , asking for information on suppliers of suitable apparatus for demonstrating the properties of Xrays to his pupils at the College . The earliest surviving Xray photograph in the College collection dates from 1897 ; as might be expected this is a skeletal image of a hand ; whose hand is not known ( Figure 1 ).
The use of Xrays for imaging broken bones was the early application , and folklore has it that , before the Royal Hampshire County Hospital got its own Xray set , patients with broken bones were sent down from the Hospital to Science School for Xrays . This may possibly have happened , on occasion , as many hospitals did not get Xray facilities until the First World War .
Fig . 2 : Large induction coil by Max Köhl of Chemnitz , supplied in 1903 . The coil is 130 mm in diameter .
Fig . 3 : Circuit layout of the Xray apparatus .
The high voltage power source consisted of a large induction coil , supplied by Max Köhl in 1903 , ( Figure 2 ) whose primary was supplied with currents of up to 10 A , from a bank of 2 V lead-acid accumulator cells ( 24 V to 36 V ). The original leaf spring “ make & break ” device had long since failed and had been replaced by an example of “ Butt ’ s mercury interrupter ” which was capable of switching much larger currents . The output of this induction coil , which could produce sparks 10 cm to 12 cm long , was applied across the anode and cold cathode ( no heated filament ) of a highly evacuated glass discharge tube as shown in Figures 3 & 4 . The anode of the tube is mounted at 45 o so that the Xray beam emerges perpendicular to the electron beam .
Butt ’ s mercury interrupter ( Figure 5 ) is an interesting piece of kit . The cast iron pot at the base contains a pool of mercury . The lid is an insulator from which various metal contacts hang . Also mounted on the lid is a motor driving the rotating impeller ( Figure 6 )
5