Cathode rays (also called an electron beam or e-beam) are streams of electrons observed in vacuum tubes.
 If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass behind of the positive electrode is observed to glow, due to electrons emitted from and traveling away from the cathode (the electrode connected to the negative terminal of the voltage supply).
 They were first observed in 1869 by German physicist Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein "Kathodenstrahlen", or cathode rays.
Ernst J. L. Gehrcke (1 July 1878 in Berlin – 25 January 1960 in Hohen-Neuendorf) was a German experimental physicist.
 He was director of the optical department at the Reich Physical and Technical Institute.
 Concurrently, he was a professor at the University of Berlin.
 He developed the Lummer–Gehrcke method in interferometry, he discovered anode rays, and he developed the multiplex interferometric spectroscope for precision resolution of spectral-line structures.
 As an anti-relativist, he was a speaker at an event organized in 1920 by the Working Society of German Scientists.
 He sat on the board of trustees of the Potsdam Astrophysical Observatory.
 After World War II, he worked at Carl Zeiss Jena, and he helped to develop and become the director of the Institute for Physiological Optics at the University of Jena.
 In 1949, he began work at the German Office for Materials and Product Testing.
 In 1953, he became the director of the optical department of the German Office for Weights and Measures.
An anode ray (also positive ray or canal ray) is a beam of positive ions that is created by certain types of gas discharge tubes.
 They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886.
 Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry.
The Shy Tory Factor is a name given by British opinion polling companies to a phenomenon first observed by psephologists in the early 1990s.
 They observed that the share of the electoral vote won by the Conservative Party (known colloquially as the 'Tories') was significantly higher than the equivalent share in opinion polls.
 The accepted explanation was that so-called "shy Tories" were voting Conservative after telling pollsters they would not.
 The general elections held in 1992 and 2015 are examples where it has dramatically affected the overall result, but has also been discussed in other elections where the Conservatives did unexpectedly well.
 It has also been applied to the success of the Republican Party in the United States.
The ethynyl radical (systematically named λ-ethyne and hydridodicarbon("C"—"C")) is an organic compound with the chemical formula C≡CH (also written [CCH] or C2H ).
 It is a simple molecule that does not occur naturally on Earth but is abundant in the interstellar medium.
 It was first observed by electron spin resonance isolated in a solid argon matrix at liquid helium temperatures in 1963 by Cochran and coworkers at the Johns Hopkins Applied Physics Laboratory.
 It was first observed in the gas phase by Tucker and coworkers in November 1973 toward the Orion Nebula, using the NRAO 11m radio telescope.
 It has since been detected in a large variety of interstellar environments, including dense molecular clouds, bok globules, star forming regions, the shells around carbon-rich evolved stars, and even in other galaxies.
Pierre Polinière (8 September 1671, Coulonces, France – 9 February 1734, Coulonces, France) was an early investigator of electricity and electrical phenomena, notably "barometric light", a form of gas-discharge light, which suggested the possibility of electric lighting.
 He also helped to introduce the scientific method in French universities.
Eugen Goldstein (5 September 1850 – 25 December 1930) was a German physicist.
 He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton.
International Day of No Prostitution (IDNP) is an awareness day that was first observed in 2002.
 Locations at which IDNP was observed in its inaugural year included the San Francisco Bay Area of California, United States and Melbourne, Victoria, Australia.
 The day is celebrated annually on October 5 as a manner of opposing prostitution.
 In 2005, the University of the Philippines Institute of Human Rights and the Asia-Pacific chapter of the Coalition Against Trafficking in Women (CATW) organized an IDNP event at which they discussed the Anti-Trafficking in Persons Act of 2003.
 In 2008, there was an IDNP candlelight vigil in Phoenix, Arizona.
 The vigil took place again in 2010, and city leaders and former prostitutes were among the participants.
 In 2010, CATW observed IDNP by opposing the decision in "Bedford v. Canada" to strike down Canada's anti-prostitution laws.
 A group of former human trafficking victims and sex workers in Canada also opposed the striking down of these laws; they picketed a courthouse in downtown Toronto, Ontario in recognition of IDNP.
 Picketers included Natasha Falle, Trisha Baptie, Bridget Perrier, Katarina MacLeod, and Christine Barkhouse.
 In 2011, People Working Against Prostitution, an organization in the Philippines, expressed their disappointment that the Cagayan de Oro city council did not host any events in recognition of IDNP.
A Wien filter also known as velocity selector is a device consisting of perpendicular electric and magnetic fields that can be used as a velocity filter for charged particles, for example in electron microscopes and spectrometers.
 It is used in accelerator mass spectrometry to select particles based on their speed.
 The device is composed of orthogonal electric and magnetic fields, such that particles with the correct speed will be unaffected while other particles will be deflected.
 It is named for Wilhelm Wien who developed it in 1898 for the study of anode rays.
 It can be configured as a charged particle energy analyzer, monochromator, or mass spectrometer.
X-radiation (composed of X-rays) is a form of electromagnetic radiation.
 Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×10 Hz to 3×10 Hz) and energies in the range 100 eV to 100 keV.
 X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays.
 In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen, who usually is credited as its discoverer, and who had named it "X-radiation" to signify an unknown type of radiation.
 Spelling of "X-ray(s)" in the English language includes the variants "x-ray(s)", "xray(s)", and "X ray(s)".

Question: What was the German scientist who first observed Anode rays also an early investigator of?
Answer: discharge tubes