January 6, 1910] 



NA TURE 



297 



below the freezing point, zero being thus determined. If 

 the tube is not cylindrical, but conical, an investigation 

 of the dimensions of the tube is made according to the 

 method described in the introduction, the result obtained 

 being the relation between the length of that part of the 

 tube enclosing the seven-eighths of the cubic contents nearest 

 the boiUng point and the whole length which is to be 

 employed for the 60° ; in the example which Romer takes 

 the conditions are such that the length of the tube between 

 the boiling point and the freezing point must be divided 

 into 52-2 equal parts, 78 parts to be added below the 

 freezing point, zero thus being obtained. In using such a 

 thermometer with a conical tube, it is necessary to have 

 a table giving the readings in terms of degrees ; thus the 

 reading 7-8 on the length of the tube meant, in terms of 

 Romer's thermometer, 7-5°, 15-563 meant 15°, &c. 



Three questions naturally arise when we see that 

 Riimer used so much of his limited time in constructing 

 on " original " thermometer : — (i) Is this interest in any 

 way connected with the rest of his scientific or practical 

 work ? (2) Did he use the thermometers thus constructed 

 for systematic measurements? (3) Have his new ideas in 

 this line contributed anything to the improved construc- 

 tion of thermometers on the whole? In " Adversaria " 

 there are indu^table indications that the first two ques- 

 tions are to be answered in the affirmative ; he gives very 

 excellent results of experiments on " the change of length 

 in metals caused by cold and heat," and, furthermore, there 

 is a sketch of an .apparatus for comparative measurements 

 of the expansion of gases and liquids when exposed to 

 heat, and some good results of these measurements. There 

 is also, as already mentioned, a series of measurements 

 made with the new thermometer of the temperature of 

 the air in Copenhagen during the winter of 1709. These 

 measurements are of special interest, and are mentioned 

 several times in the literature of foreign countries. The 

 winter of 1709 was very severe. In an article in Phil. 

 Tjans., \o. 324, 1709, W. Derham writes, in " The 

 History of the Great Frost in the last Winter," about the 

 conditions in Denmark : — " Dr. Woodward tells me, that 

 in a lettre, he received from the learned Mr. Otto Sperling 

 from Copenhagen, dated April 6, 1709, he calleth it Hyems 

 Atrocissima. knA I find it noted in the Minutes of the 

 Royal Society of May 4, 1709. That Dr. Judichar said 

 the ice was frozen in the harbour of Copenhagen 27 inches, 

 and that .April g N.S. people had gone over between 

 Schone and Denmark on the ice. Which accounts give me 

 a better opinion of some papers I have by me which 

 were shew'd to the Society, concerning the frost at Copen- 

 hagen pretended to be taken from the observations of Mr. 

 Romer. I should not entertain any the least distrust of the 

 accuracy either of the instruments or observations of that 

 eminent person were I sure they were his. But there are 

 some passages and hints in those papers that lessened 

 others as well as my opinion about them. 'Tis said there 

 ' That such a frost hath not been known in the memory 

 of man of these countries and that ' ihe frost on January 7 

 and Fehruary 23, 170;;, did very nearly approach ihe Point 

 of Artificial Freezing.'" If we now look at the table 

 of Romer's temperature observations from 1708-9 which 

 is found in "Adversaria," it will be seen that it begins 

 December 26, 1708, and continues until April 9. 1709, only 

 that after April i there are not observations for every day, 

 and this is no doubt due to the fact that the table is only 

 calculated to show temperatures under 8°. The remarks 

 along the margin are written in Horrebnw's hand. The 

 first remark is? — " So Romer had changed his first plan." 

 The meaning of this is, as may be seen from Horrebow's 

 other remarks in " Adversaria," that he thinks that Romer 

 had placed 8 at the melting point instead of 7J as earlier. 



Now the table shows that on February 23, exactly the 

 date which Derham especially mentions, the thermometer 

 went down to about Romer's zero. It is important to note 

 the exact wording of Derham's remark, " that the frost. 

 February 23. 170^. came near the temperature for artificial 

 freezing." So it is evidently taken for granted here that 

 Romer's zero was the temperature of a freezing mixture, 

 a fact which Derham must have obtained from the report 

 sent from Denmark, since he was not acquainted with 

 1 Emphasised by K. M. 

 NO. 2097, VOL. 82] 



Romer's scale. This remark is of special importance for 

 the question as to whether, and if so through what 

 channels, Romer's thermometer has had any widespread 

 influence. The answer is in the affirmative, and the way 

 in which Romer exercised a wide influence was through 

 his influence on Fahrenheit. I shall now proceed to prove 

 that such an influence was exercised by Romer. 



In the first place, there are some direct statements about 

 this matter. The most important is by Boerhaave, who, 

 in writing about Fahrenheit's thermometer, says : — " Now 

 ir is said that the eminent mathematician Romer in the 

 year 9 of this century observed in Danzig a winter-cold 

 down to the first degree of this same thermoscope, of 

 which he himself was the first inventor. Then he increased 

 it with 32° below the freezing-point." 



So here it is stated quite distinctly that Romer was the 

 first inventor of Fahrenheit's thermometer ; and importance 

 is to be attached to Boerhaave's words about this matter, 

 because he was closely connected with Fahrenheit, who 

 had constructed his thermometers, and whose skill as an 

 instrument-maker and experimenter he often speaks of in 

 terms of praise. That Romer should have made measure- 

 ments in Danzig in 1709 must be a mistake, which can 

 easily be accounted for by the fact that there are accounts 

 of measurements made in Danzig the same winter with a 

 similar thermometer. At least, I have not been able to 

 find any indications that Romer was in a foreign country 

 at the time mentioned, and his many official duties, his 

 delicate health, and that very list of temperatures for 

 Copenhagen which was sent to the Royal Society make it 

 improbable that he was away from home. 



On the other hand, it is related in a biography ' of 

 Fahrenheit, written four years after his death, that after 

 1706 he made many difficult journeys by sea and by land, 

 and conferred with the most famous mathematicians in 

 Denmark and Sweden ; it is probable that Ole Romer was 

 one of the famous men whom he visited, and then Fahrenheit 

 must have visited him just at the time when the " original 

 thermometer " was used ; if Boerhaave's statement is 

 correct, it must be possible to trace Romer's influence on 

 Fahrenheit's thermometers. What Fahrenheit could learn 

 from Romer was chiefly the principle of the two fixed 

 points as a basis for the thermometer scale. According 

 to Fahrenheit's own brief account ° of his method in the 

 construction of his thermometers, he does, in fact, use 

 fixed points as a basis for his scale, but he mentions 

 three : the temperature of the freezing point, the tempera- 

 ture of a cold mixture, and the temperature of the healthy 

 human body ; the last, however, is apparently only used 

 as a sort of check, because Fahrenheit does not wholly 

 relv on the constancy of the temperature of the cold mix- 

 ture. Now Fahrenheit probably took the two fixed points 

 from Romer, since the zero of Romer's scale, as was 

 evident from Derham's account, was identified with the 

 temperature of a cold mixture, and it appears th.at the 

 scales of several of the oldest of Fahrenheit's thermometers 

 have the same numeration as Romer's. These thermo- 

 meters are mentioned in various places ; Grischow ' especi- 

 ally has a full comparison of the somewhat varying scales 

 which Fahrenheit used at different times. 



.According to Grischow * and others," Fahrenheit is said 

 to have confided to his tutor in mathematics, Barnsdorf 

 (from Rostock), the secret of the method of division used 

 on his thermometer, which he maintained was such that 

 anyone who knew it could construct thermometers which 

 agreed. Grischow writes that this happened " circiter 

 1712 and 1713 nise jam ante." Shortly after th.at Fahren- 

 heit travelled to Halle and Leipzig, and then Barnsdorf, 

 in conjunction with a colleague named Lange, tried to 

 construct thermometers after the instructions. The scale 

 on these was somewhat different from that on the thermo- 

 meters which were generallv known later as F.ahrenheit's. 

 and we read about Barnsdorf that he nrobably retained 

 "the older or oldest Fahrenheit division." Now from the 

 table it appears that Barnsdorf's thermometers have yh at 



1 Altpreuss. Monatsschr'.ft, ii., 1874, contains a fragment edited by E. 

 SfrehleU. 



2 Phil. Trans. London, vo'. xxxili., 1724. np. 73-84. 

 ^ Miscell. Eerolienses, t. vi. (printed 17^7)- 



4 Loc. cil.. p. 271. 



5 Cotte, "Traitede Met^orologie," 1774, p. 129. 



