History tf Platina Pyrometers. 147 



descendere, prout aer sphterse DE magis magisque incalescit." Page 

 89. App. 



This amiable author then proceeds to consider who first invented the 

 thermometer. " Ecquisnam primus fuerit thermoscopii inventor, vix 

 constat. Aliqui, quos inter supra laudatus Lana, Roberto Fludd seu a 

 Fluctibus id honoris tribuunt, Samveli Reyhero autem, Mathem. in alma 

 Kilonensi Prof. P. videtur prima inventio deberi Drebbeho." P. 89, 90-. 



These passages, which we purposely leave untranslated, settle for ever 

 the invention of the differential thermometer; and as we and many 

 others know that Mr. Leslie has read and studied the Collegium Curio- 

 sum of Sturmius, we trust that he will avail himself of the first oppor- 

 tunity, both in his lectures and in his writings, of restoring voluntarily to 

 that amiable and learned Professor the honour of an invention which so 

 unquestionably belongs to him. 



In a future number, we shall proceed to rectify the history of the 

 Hygrometer, the Photometer, the JEthrioscope, the Drying and the 

 Freezing processes, &c. &c. &c. of Professor Leslie, which we trust we 

 shall illustrate as successfully as we have done that of the differential 

 thermometer. 



In the mean time, we proceed to other claims. 



2. DanieIVs Platina Pyrometer, partly anticipated by M. Guyton. 



Our scientific readers are no doubt well acquainted with the merits 

 of Mr. Daniell, to whom we owe many excellent inventions and admira- 

 ble memoirs on scientific subjects- In the year 1821, he published in 

 the Quarterly Journal of Science, (vol. xi. p. 309.) a description of a py- 

 rometer for high degrees of heat, which eonsisted of a platina bar placed 

 within a tube of black lead earthen ware. The expansion of the bar 

 was indicated upon a circular scale, through the intermedium of a pla- 

 tina wire acting upon the axis which carried the index. 



Mr. Daniell does not seem to have been aware that M. Guyton had 

 exhibited to the National Institute in 1803 a similar instrument, con- 

 sisting of a rod or plate of platina, placed in a groove formed in a cake 

 of hardened white clay. One of the ends of the platinum bar presses 

 against a bended lever of platina, whose longest arm forms an index to a 

 graduated arc. 



The principle of these instruments is the same, both of them depend- 

 ing on the difference of the expansions of pottery and platina ; but they 

 differ in this, that the whole of Guy ton's instrument is put into the fur- 

 nace, whereas, in Mr. Daniell's, the platinum bar is alone exposed to 

 the heat, the index and scale being kept at a distance from it. See the 

 Ann. de Chim. No. 138, vol. xlvi. p. 274, Nicholson's Phil. Journ. vol. vi. 

 p. 89, and the Edinburgh Encyclopaedia, Art. Pyrometer, vol. xvii. p. 

 215, where both of them are described. 



3. Mr. Nicholas Mill's Pyrometer, anticipated by Dr. Ure. 



In the year 1824, Mr. Nicholas Mill published in the Monthly Medi- 

 co~Chirurgical Review, $c. a drawing and description of a pyrometer, 



