Context: The Warnerke Standard Sensitometer consisted of a frame holding an opaque screen with an array of typically 25 numbered, gradually pigmented squares brought into contact with the photographic plate during a timed test exposure under a phosphorescent tablet excited before by the light of a burning Magnesium ribbon. The speed of the emulsion was then expressed in 'degrees' Warnerke (sometimes seen as Warn. or °W.) corresponding with the last number visible on the exposed plate after development and fixation. Each number represented an increase of 1/3 in speed, typical plate speeds were between 10° and 25° Warnerke at the time.

Question: What consists of 25 pigmented squares touching a plate below a phosphorescent tablet under the light of a burning Magnesium ribbon?
Answer: The Warnerke Standard Sensitometer

Question: What do degrees Warnerke measure?
Answer: The speed of the emulsion

Question: How much speed is associated with each degree Warnerke?
Answer: an increase of 1/3 in speed

Question: What were usual ranges of Warnerke speeds? 
Answer: between 10° and 25° Warnerke

Question: What does the last exposed number on the plate represent? 
Answer: 'degrees' Warnerke

Question: The Warnerke Standard Sensitometer has 25 opaque what?
Answer: Unanswerable

Question: What measures the number of pigmented squares on the photographic plate?
Answer: Unanswerable

Question: Degrees Warneke represented the first what?
Answer: Unanswerable

Question: What was the range of the number of squares in a Sensitometer?
Answer: Unanswerable

Question: Each number represented a decrease of what?
Answer: Unanswerable