1912:  Sir Joseph John (J.J) Thomson utilized an instrument consisting of parallel magnetic and electric fields to deflect a beam positive ions [Phil. Mag. 6 (1912) 752-767].  By using a photographic plate to record the trajectory of the ions Thomson was able measure the extent to which the ions were deflected.   Knowledge of the strengths of the magnetic and electric fields allowed Thomson to calculated the mass-to-charge ratios of the positive rays.  Because of this achievement, J.J. Thomson is widely considered the “Father of Mass Spectrometry”.  Thomson received more wide spread acclaim for his previous work discovering and characterizing the electron, for which he received the Nobel Prize in Physics in 1906 and was knighted in 1908.  Additionally, Thomson was know for his outstanding teaching abilities, mentoring eight future Nobel Laureates in Physics including his son George.