Mr. F. D. Brown's Notes on Thermometry. 61 



broken up into small fragments, which were well mixed up, 

 so as to render the whole perfectly uniform in character. 

 One of the tin pots, which we will call A, was filled with 

 some of this ice, which had been washed in a funnel with 

 ordinary water ; A was then filled up with water, so as to 

 form a mixture in which the ice largely predominated. A 

 second tin, B, was filled with some more of the ice, which 

 had been washed with ordinary water in the same way; B, 

 however, had holes at the bottom, and the water formed by the 

 fusion of the ice thus drained away. A third tin, C, contained 

 some of the same ice, which had been washed in a funnel with 

 distilled water, and then mixed with distilled water in the 

 same way as in A the ice was mixed with ordinary water. 

 In a fourth tin, D, which was provided with holes, some ice 

 was placed which had been washed with distilled water. 

 Finally a quantity of distilled water was artificially frozen, 

 the ice broken up into small pieces, washed, and mixed with 

 distilled water in a fifth tin, E. A thermometer with a long 

 narrow bulb, and with a stem divided into millimetres, was 

 carefully inserted into each tin in succession, and readings 

 taken with a cathetometer. About 17 millim. of the scale 

 were equivalent to one degree Centigrade. In A the readings 

 soon became constant at l o, 00 ; in B the readings varied con- 

 siderably for about half an hour, but finally became constant 

 at 1 0, 12 ; in C the thermometer became rapidly constant at 

 1 0, 16 ; in D the readings became constant after a short time 

 at l o, 06 ; in E the readings did not vary after the first four 

 or five minutes, remaining at o, 64. 



At the end of these observations, which occupied nearly two 

 hours, the thermometer was replaced in A, where the mercury 

 rapidly assumed the same position as before, viz. 1°'00. Seeing 

 that, with the exception of E, the greatest difference in the 

 readings does not amount to o, 01 C, we may fairly draw the 

 following conclusions: — First, that a constant temperature is 

 more rapidly and certainly obtained with a mixture of ice and 

 water than with ice alone ; secondly, that the temperature 

 thus obtained is really that of melting ice ; thirdly, that it is 

 preferable to wash and mix the ice with distilled water, 

 ordinary water tending to lower the temperature, though to an 

 insignificant extent. 



With the view of seeing whether different varieties of ice 

 gave the same results, two specimens of block ice and one of 

 the rough thin ice collected in winter near London were 

 obtained, while two cylinders of distilled-water ice were arti- 

 ficially produced. These were all broken up separately into 

 small pieces, washed with distilled water, and then mixed with 



