Notices respecting New Books. 329 



Light and air are regarded by our author as the two great powers 

 which uphold the universe. In his opening paragraph he naively 

 inquires, " Is not the agitation of boiling w^ater caused by air which 

 enters through the bottom of the vessel, and which rising up 

 through the water causes the bubbling called boiling ? " We really 

 imagined that Mr. Woodhead, in stating the case thus, had conde- 

 scendingly placed himself in the position of some interesting little 

 prattler, standing at his nurse's knee, and putting to the said nurse 

 the above philosophical query ; and that Mr. Woodhead, in his own 

 benign wajr, was going to set the little questioner right. But no — 

 this is Mr.Woodhead's ow n opinion. He believes that tl-e air actually 

 enters in the manner described ; he believes that light is air in a state 

 of radiation ; and his theory of caloric is, that light penetrates bodies 

 and makes way for the admission of air into them ; and it is the 

 expressed air of a red-hot piece of iron, which, when it is immersed 

 in water, causes the ebullition, repulsion, expansion, steam and 

 hissing. 



It is sometimes mournful to observe how the inventions of one 

 age render the pains and labours of the preceding one valueless. 

 The ponderous aqueducts of ancient Rome are rendered useless by 

 the application of the simplest laws of hydraulics ; canals are super- 

 seded by railways ; and the Manchester cotton-spinner has often to 

 cast sound and costly machinery aside, to avail himself of some new 

 invention. Philosophic endeavour is doomed, in the eternal progres- 

 sion of things, to share a similar fate ; ai!d it is with a certain exalted 

 sorrow that we contemplate the efforts of Mr. Woodhead's predeces- 

 sors. Upwards of thirty years ago Colonel Sabine took up his cold 

 and perilous post on Melville Island to make pendulum experiments, 

 and deemed himself lucky in getting away from the place, after a 

 winter's exile, without any accident save the loss of five frost-bitten 

 fingers by an incautious artilleryman. But his troubles might have 

 been spared had our latter- da)' genius been present to tell him that 

 he was pursuing a phantom, and beating the air, in another sense 

 than the mere literal one, when he set his pendulums agoing. The 

 retardation of the pendulum and the decrease in the intensity of 

 gravitj' in the equatoreal regions, quoth Mr. Woodhead, are attribu- 

 table to the increased density of the atmosphere in these regions. 

 His theory is, that the centrifugal force arising from the earth's 

 diurnal rotation causes an accumulation of air, and a consequent in- 

 crease of pressure at the equator, — not at all regarding the mathe- 

 matical fact, that were the motion of the earth seventeen times 

 quicker than at present, poor Mr. Woodhead himself, if placed at 

 the equator, would dance upon nothing, and exercise no practical 

 pressure at all. 



But, to Mr. Woodhead's mind, the dip of the magnetic needle 

 affords still stronger and more striking evidence of the above arrange- 

 ment of the atmosphere. In the direction of the ])oles the atmo- 

 spheric resistance is least ; the needle points in the direction of least 

 resistance, and hence its polarity. What will Carl Friedrich Gauss 

 say to this ? Here is also a morsel for the geologist : — The increase 

 of heat observed as we descend a shaft is caused by the superincum- 



