172 NEGRETTI AND ZAMBRA, HOLBORN VIADUCT, B.C., 



400 Fig. 400 and fig. 400* are other arrangements of this Thermometer, made by 



Negretti and Zambra under special instructions from Professor Everett, for 

 the Committee of the British Association on Underground Temperatures, 



401 Fig. 401 is the Thermometer, enclosed in a Glass Tube or Sheath, fitting into 



a hinged Copper Protecting Case ("Well Thermometer), as seen in fig. 400*. 



Price, 1 10 



402 Fig. 402 is a Thermometer of very Slow Action for taking direct Earth 



Temperatures, The bulb of this Thermometer is shown in its Glass Sheath 

 surrounded by a good non-conducting substance as suggested by Professor 

 Everett. The Thermometer being lowered down to the desired depth by a 

 cord, is allowed to remain a considerable time in the earth so as to attain 

 the existing Temperature. It is then withdrawn quickly, and the reading 

 noted, the non-conductor around the Bulb preventing any rapid change 

 taking place for a sufficient time to ensure accuracy. Price, 18 6 



See also pages 35 and 43. 



The Range of Scale of these Maximum Thermometers can be varied to suit the 

 requirements of the experiments to be carried out. 



At the meeting of the British Association in 1872 (Brighton), Prof. Phillips when speaking on the 

 subject of the use of his own form of Thermometer for ascertaining underground temperatures, said> 

 " There would be difficulty in using such instruments where the light was bad, and he thought the 

 instrument exhibited by Prot'. Everett (Negretti's Vertical Thermometer; was better adapted to the 

 purposes of the Committee." 



Beneath the surface of the Earth the Temperature increases at the rate of 1 

 Fah. for every sixty feet. Another authority states it 1 Fah. for every forty-nine 

 feet. The temperature for the first sixty feet is influenced by the Seasons. 



In deep caverns, the effect of the great heat of summer has been only felt at 

 mid-winter, and vice-versa, the cold of winter only reaches them at mid-summer. 



The subjoined list of Temperatures compiled from various reliable authorities 

 is inserted as well illustrating the above observations. 



Artesian Well, Hanwell, 290 ft. deep, 55 9 . 

 Grotto del Cane, Italy. 68. 

 Earth Yokutsk, 50 ft. deep, 18. 

 Hecla Earth at Summit, 153. 

 Geyser Springs, Iceland, 179. 

 Thermal Spring, Tajurah and Shoa, 152. 

 Thermal Spring, Island of Lucon, 174. 

 Volcanic Mud, Jorullo, South America, 203. 

 Ournastok Spring, Greenland, 103. 

 Comagillas, Mexican Springs, 205. 

 Eaux Bonnes, Pyrenees, 89. 

 Aix-la-Chapelle Spring, 



Maximum Temperature. 180. 

 Aix-la-Chapelle Spring, Spa, 143. 

 Baden Baden Springs, 



Maximum Temperature, 157. 



Bagneres-de-Bigore Spring, 123. 



Mariana Springs, South America, 138. 



Wiesbaden Spa, 149. 



San Germano Bath, Naples, 181. 



Buxton Spring, 82. 



Matlock Spring, 66. 



Bristol Spa, 66. 



King's Bath, Bath, 114. 



Hot Pump, Bath, 116 Q . 



Bath Springs, Maximum Temperature 117. 



supposed depth, 3,350 ft. 

 Monkwearmouth Mine, 1,500 ft. deep, 72. 

 Consol Mine, Cornwall, 1,740 ft. deep, 93. 

 Cumberland Coal Mine, 600 ft. deep, 66. 

 Salt Mine, Cracow, 730ft. deep, 50 9 . 

 Guanaxato Mines, 1,700 ft. deep, 99 9 . 



On page 48 of Mr. Scott's Book on Elementary Meteorology will be found a Chronoisothermal Diagram 

 representing the Monthly Mean Temperature at Greenwich for every hour of the day through the range of 

 years 1849 to 1868. " This diagram was devised by M. Leon Lalanne it exhibits many most interesting 

 facts in connection with the climate of London, amongst others, that the highest mean temperature (70) 

 only occurs in the latter part of July and between one o'clock and half-past three p.m., and the lowest 

 mean temperature (38) is observed during the night-time from about January 5th, to March 20th. 



Also it will be seen that the coldest time in summer is from three to five in the morning, while in 

 winter there is not much change between four in the afternoon and eleven in the morning. It will be also 

 noticed how much colder the Spring equinox is than the Autumnal, for on April 1st the temperature 

 ranges from 40 to 50 F., while on October 1st the range is from 50 to 61 F." 



t Prof. Everett, D.L.C., of Belfast. 



