4*4 



SCIENCE PROGRESS. 



the tube, and every twelfth division was marked by the use 

 of a larger bead or one of a different colour. Further 

 information as to these thermometers, some of which were 

 sent to the Queen of Poland by the Grand Duke of 

 Tuscany in 1657, and thence went to Paris, has recently 

 been published by M. Maze {Comptes Re/idus, vol. cxx., 

 p. 732, and vol. cxxi., p. 230). 



The difficulty of fixing- the zero and the distance 

 between the divisions of the thermometer was early recog- 

 nised, and the want of uniformity was probably due to the 

 fact that chemists were not aware that the freezing and 

 boiling points of liquids were constant. Hooke, however, 

 in 1665, described in his Micrographia, p. 38, a spirit ther- 

 mometer having the zero at the freezing point of water, 

 which he apparently recognised as constant. Boyle also 

 proposed this standard, recommending the use of distilled 

 water, as he was persuaded that waters of different origin 

 congealed at different temperatures (see Boyle s Woi'ks, 

 abridged by Shaw, vol. i., p. 579). As an alternative, he 

 proposed the congealing point of oil of aniseed as the zero. 



In 1692 Mr. Edmund H alley, Secretary of the Royal 

 Society (see Pkil. Trans., 1692-3, vol. xvii., p. 650), pub- 

 lished an important paper on the construction of ther- 

 mometers "for use at any place without adjusting by a 

 standard". He stated that he was not aware of anv ther- 

 mometers which had been graduated except as the work- 

 man's fancy dictated, although they were usually graduated 

 from a fixed point such as the freezing point of water, or 

 " the point where the spirit stands when it is so cold as to 

 freeze oil ol aniseed ". After discussing the relative merits 

 of various liquids, and mentioning that mercury might be 

 most properly used were its expansion more considerable — 

 probably the first mention of mercury thermometers — he 

 recommended spirit of wine as the best. 



In 1694 Professor Renaldini of Padua suggested the 

 fixation of unity by the temperature of a mixture of eleven 

 parts of cold water with one part of boiling water, the 

 second degree being obtained by mixing ten parts of cold 

 with two parts of boiling water, and so on. In 1701 New- 



