526 Dr. P. Riess on the Law of Electric Discharge. 



In my investigations of heat, it was natural that I should 

 submit the instruments and processes employed by the author 

 to a rigid criticism, and reject them when they did not stand 

 the test. It is not true that I ascribed the unsuccessful ex- 

 periments of Sir W. Harris to the faulty arrangement of his 

 thermometer. My words, that the experiments were not made 

 with the necessary care (Pogg. Annalen, vol. xl. p. 335), cannot 

 be referred to the thermometer, as immediately afterwards, in 

 the description of my instrument, I say that the bulb (con- 

 sequently the most essential portion) was arranged according to 

 Harris's description. A greater simplicity and sensibility of 

 the thermometer certainly appeared to me to be desirable. 



My objections, if my memory is correct after so long a time, 

 referred to the totally inadmissible process of the author of 

 effecting the discharge of the battery by means of a ball which 

 was obliged to shatter a glass disc lying iipon the battery. I 

 was compelled at once to reject the " unit-jar " of Sir W. Harris, 

 as I perceived that during the charging the unit of the amount 

 of electricity would continually decrease, and that the more 

 rapidly the smaller the charged battery is. I adopted another 

 method of measuring the amount of electricity, because it was 

 justified by theory and proved by practice, and in employing it I 

 did not forget to state that it was described by Haldane in 1800. 

 I have hitherto supposed that I was the first to make a practical 

 use of this process, but I am now informed by Sir W. Harris 

 that it had already been employed by him in 1830. My error 

 is very excusable, for it was difficult to believe that a physicist 

 should have been acquainted with a correct method of measure- 

 ment, and have rejected it in favour of an incorrect one. I have 

 sufficiently acknowledged the merits of Sir W. Harris in the 

 improvement of the electrical thermometer, by frequently de- 

 scribing and once figuring it in the form which he represents as 

 the most perfect. But I must affirm that he is still unacquainted 

 with the use of the thermometer in the demonstration of the 

 laws of electrical heat, as he is still unaware of the necessity 

 of employing a calculation to render the data capable of com- 

 parison when the wires are changed in the thermometer. Nor 

 can I at all agree with Sir W. Harris in his favourite idea, that 

 his thermometer is a peculiar instrument essentially different 

 from Kinnersley's. The disadvantageous vertical position of 

 the tube with the fluid is common to both instruments. The 

 air-holder is globular in the one and cylindrical in the other; in 

 the one the wire is extended by the fastening of its two ends, 

 in the other it is fastened to the lid of the air-holder, stretched 

 by a weight and lowered into the air-holder. These are differ- 

 ences of construction which may perhaps affect the coiivenience 



