426 Mr. C. Chambers on Terrestrial Magnetism. [May 13, 



Further confirmation of the facts stated as to the modification of arterial 

 tension may be found in Marey's work, ' De la Circulation du Sang,' 

 published in Paris in 1863. In that book the author ascribes the uni- 

 formity of the heat in the internal parts to the same cause as the author of 

 the present paper ascribes the variations. 



The fact observed by Dr. W. Ogle in the St. George's Hospital Reports 

 for 1866, and by Drs, Ringer and Stewart in a paper read before the Royal 

 Society this year, that the temperature falls at night, and is lowest at from 

 12 to 1 a.m., and begins to rise after that time, is simply explained on 

 the theory given above ; for it depends on the custom of Englishmen going 

 to bed at about that hour, and thus giving a large amount of heat to the 

 cold bedclothes, which at first is expended in warming the sheets &c, 

 while later on in the night the bedclothes are warm, and therefore the 

 body has only to make up for the heat diffused. 



Other natural phenomena can be similarly explained. Thus, on a cold 

 day, the effect of sitting with one side of the body in the direct rays of a 

 fire is to cause the other side to feel much colder than if there was no 

 fire at all, because the fire lowers the tension over the whole body, and 

 supplies heat to the full cutaneous vessels of one side, while the other side, 

 being equally supplied with blood in the skin, does not receive heat, but 

 has to distribute it rapidly to the cold clothes &c. 



II. " Observations of the Absolute Direction and Intensity of Ter- 

 restrial Magnetism at Bombay." By Charles Chambers, 

 Esq., Superintendent of the Colaba Observatory. Communi- 

 cated by Lieut-General Sabine, R.A., President. Received 

 April 5, 1869. 



(Abstract.) 



The observations made by the author were of the three usual elements 

 — the Dip, Declination, and Intensity of the Horizontal Component of the 

 Force. They were taken with instruments supplied to the Colaba Obser- 

 vatory in the year 1867 through the Kew Committee of the British Asso- 

 ciation, after having been tested at the Kew Observatory. The dip-circle 

 was made by Barrow of London, and is furnished with two needles ; the other 

 instrument, the unifilar magnetometer, which serves both for observations 

 of declination and horizontal force, was made by Elliott Brothers of Lon- 

 don. The results of the observations for dip only have as yet been received 

 from the author. 



A complete observation consists of thirty-two readings, each end of the 

 needle being read twice in each different position of the needle and circle ; 

 and the mean of the thirty-two is taken as the result of the observation. 

 The observations were 1 78 in number, commencing on the 29th of April 

 1867, and extending to the 29th of December 1868. They were gene- 

 rally taken, with the two needles alternately, on particular days of the 



