that in the present experiment there was a loss of between three and
four inches of nitrogen to be sought in the residuum which had been
heated in the metallic tube. But when the tube was opened, nothing
was found but potash that had been fused, and a small quantity of
potassium sublimed into its upper part; so that in the place of the
nitrogen nothing was found but oxygen contained in the potash,
which, together with a small excess of hydrogen, may amount to the
Weight of the nitrogen lost.
In other experiments five grains of the olive—coloured ammoniacal pyrophorus, formed by potassium, yielded by mere heat, or by oxygen, three fourths of an inch of nitrogen; but by water they evolved one fifth of hydrogen, and 31‘; of ammonia, which by estimate contain 1% of nitrogen.
If the nitrogen is to be considered as converted into oxygen and hydrogen, it must be regarded as containing much more oxygen than water; and if we do not adopt this supposition, Mr. Davy considers the only alternative tobe, that water is the ponderable matter which, under different modifications of electro-chemical existence, consti- tutes oxygen, hydrogen, nitrogen, and the nitrous compounds; but with respect to conclusions so important, and so little to be expected by any analytical chemist, it appears to Mr. Davy highly unphiloso- phical to decide in the present state of our knowledge.
Since the remarks, which the author has connected together on the present occasion, as tending, each of them, to promote the design of Dr. Croone, do not appear to bear any direct relation to each other, he divides the lectm-e into three distinct heads; the first of which contains an observation, and some experiments on the duration of muscular action. In the second he traces the origin of sea-sickness, from a mechanical cause deranging the circulation of the blood. In the third he offers a mechanical explanation of the advantages de- rived from riding, and the various modes of carriage exercise.
With regard to the duration of muscular action, the author is of opinion that each effort, apparently single, consists in reality of a great number of contractions. repeated at extremely short intervals. He infers the existence of these alternate motions, from a sound ob- served upon inscrting the extremity of the finger into the ear. The sound resembles that of carriages at some distance passing rapidly over a pavement. The sound is not perceived when the force applied to stop the ear is not muscular, unless the action of some distant muscle be communicated through some medium capable of conveying its vibrations.
With a view to estimate the frequency of these vibrations, the author contrived to imitate them by rubbing a stick, regularly notched, and placing it in such a position, that the tremor was communicated to the ear along with the muscular vibrations. The results of such
