Lunar Variations of Magnetic Declination at Bombay. 135 



but against the relaxed diaphragm — relaxed, that is, by the abdominal 

 muscles drawing down the lower ribs, and thus contracting the circum- 

 ference of the lower part of the chest. 



The intercostal muscles also contribute importantly to this result, as the 

 effect of their contraction is reversed, by the lower ribs being relatively 

 fixed during the action of the abdominal muscles. In this way both the 

 long diameter and circumference of the chest are abridged. 



10. The upper and lower costal movements in both sexes, when entirely 

 unfettered, are equal, in ordinary inspiration and in the uncontracted 

 chest. 



The costal movements, both upper and lower, are much greater in forced 

 inspiration in the male than in the female. 



In both, the lower costal movements are much abridged by compression 

 of the abdomen and lower part of the chest, while the upper costal move- 

 ments are exaggerated. 



The observed fact that women breathe more by the chest than by the 

 abdomen is due to artificial compression, and to the altered form of the 

 chest consequent on its early adoption. 



February 1, 1872. 

 Sir JOHN LUBBOCK, Bart., Vice-President, in the Chair. 



The following communications were read : — 



I. "On the Lunar Variations of Magnetic Declination at Bomba} 

 By Charles Chambers, F.R.S., Superintendent of the Colaba 

 Observatory. Received December 4, 1871. 



(Abstract.) 



This paper is in continuation of that " On the Solar Variations of Mag- 

 netic Declination at Bombay," published in the Philosophical Transactions 

 for 1869 ; but the discussion is confined to the observations of the years 186 1 

 to 1863, which alone have as yet been reduced. The point of principal in- 

 terest brought out in the discussion is that whilst the mean lunar-diurnal 

 variation is of the ordinary character, having as its principal feature a 

 double oscillation in the lunar day, its range is very small as compared 

 with the several ranges of the lunar-diurnal variations when the sun and 

 moon have several specific varieties of relative position ; and moreover, 

 although in those latter variations the double oscillation is generally pre- 

 served as a main feature, correspondence of phase in the representative 

 curves is as generally absent ; and in some cases the curves are, whilst syste- 

 matic, altogether different in character from the mean lunar -diurnal 

 variation curve. The semiannual inequality in the lunar-diurnal variation, 



VOL. XX. M 



