Noun
An instrument for indicating changes of temperature without indicating the degree of heat by which it is affected; especially, an instrument contrived by Count Rumford which, as modified by Professor Leslie, was afterward called the differential thermometer.
Source: Webster's dictionaryT.D. McGee (1988) Principles and Methods of Temperature Measurement, pages 2–4 ISBN 0-471-62767-4 The first person to put a scale on a thermoscope is variously said to be Francesco Sagredo (1571–1620) or Santorio Santorio in about 1611 to 1613. Source: Internet
Timeline 1500s * 1592–1593 — Galileo Galilei builds a device showing variation of hotness known as the thermoscope using the contraction of air to draw water up a tube. Source: Internet
The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani (1566 – 1624): the first showing a scale and thus constituting a thermometer was by Robert Fludd in 1638. Source: Internet
The difference between a thermoscope and a thermometer is that the latter has a scale. Source: Internet