boards) corresponded to 120 litre of air, while with the guide grm. of carbonic acid corresponded to 1.48 litre..

1

As the mean results obtained for the amount of carbonic acid expired sitting and while on the tread-boards, agrees so well with both of us respectively, I have thought it worth while to calculate the mechanical power developed by the combustion of the amount of carbon burnt while working the tread-boards, in excess of that consumed in the sitting posture. 17.92 kilos. were raised to a height of 128.5 millims., 45 times per minute.

Mean carbonic acid per minute on the tread-board

Per 100 kilos.

1435
0.676

Excess expired on the tread-boards...... 0.759 grm. Corresponding to 103.6 kilogrammetres (0·1285 × 17·92 × 45=103.6) of work done, or 0.00733 (103·6 : 0·759=1: ×) CO2 expired, was equal to an oxidation of 0.002 grm. carbon, capable of raising 1 kilo. to 1 metre.

From Watts' Dictionary of Chemistry (vol. iii, pp. 105 and 129) the mechanical action of one unit of heat-423-5 gramme-metres, and one gramme of carbon yields by its combustion 8080 units of heat. Therefore, 1000 grammes carbon=8080000 units of heat yielding (8080000 × 423-5) 3421880000 gramme-metres or 3421880 kilogrammetres for the mechanical action of 1 kilogramme of carbon.

The relation between the above theoretical mechanical power of burning carbon and the actual mechanical power found to be evolved in my experiments was as follows :

1000 grms.: 3421880=0·002: ×. X =6.84.

Therefore we only applied

1

6.84'

or 0-147 of the power the carbon

we burnt on the tread-boards (in excess of that consumed sitting) was theoretically able to exert.*

As to the percentage of the carbonic acid in the air expired, while on the tread-boards, it increases at the highest station in my case, and this increase is somewhat gradual from the lowest to the highest station. With the guide the maximum percentage is met with at the middle station.

The frequency of the respiration increased in my case from the lowest to the highest station, while with the guide it is slightly in

There is so little carbonic acid present in the atmosphere, especially at some altitude above the sea (M. P. Truchot, "Compt. Rend. de l'Académie,” vol. lxxvii, 1873), that its presence in the air breathed has not been taken into account in this calculation.

creased at the middle station, undergoing a marked and sudden reduc. tion at the seaside.

Water Expired from the Lungs at the Various Stations.

The third part of my paper refers to the moisture exhaled.

It was apparent at the outset that a falling off in the atmospheric pressure, from rising above the sea, would be attended with a corresponding increase of evaporation from the lungs, and a proportional cooling effect on the respiratory organs. The apparatus used for the inquiry was disposed as follows:

A tube drawn out at both ends was loosely filled with fragments of calcic chloride; it was large enough to ensure the absorption of the whole of the vapour expired in three minutes.,. One end of the tube was connected with one of my large india-rubber bags, while the other end had a ring of vulcanised india-rubber fixed round, to which the mouth was applied. A delicate spring valve (by Coxeter) was fitted into the neck of the tube next the bag, and was weighed with the tube; it effectually prevented any admission of air into the tube except that given out from the lungs. Either the tube or the bag was placed in communication with a water gauge by a neck and indiarubber tubing. Every now and then the calcic chloride was tested as to its power of retaining all the moisture; this was done by connecting another similar tube with it and weighing it after breathing through them both. No mouthpiece was used in these experiments, as moisture was found to deposit on anything interposed between the mouth and tube. The air breathed was inspired through the nose only while the whole of the air expired was driven through the tube, the nose being kept closed with the thumb and index. I found no difficulty in doing this with accuracy; great care was taken to keep the saliva from flowing into the tube together with the air expired. Except in the case of a few experiments at the summit of the Peak, I alone submitted myself to this part of the inquiry. The experiments were made by series of usually three at a time, the figures given in my table are the means of those of the different series.

The numbers actually obtained gave, of course, the weight of the moisture evaporated from the lungs, together with that of the atmospheric humidity of the air exhaled; a correction had, therefore, to be made. I determined the atmospheric humidity by means of dry and wet bulb thermometers, and the corresponding weight of moisture in a given bulk of air was taken from Glaisher's hygrometrical tables (fifth edition).

The results from these experiments have been condensed in the following table :

It was not without some trouble that a few successful determinations of the moisture expired were obtained at the highest point of the Peak, 12,200 feet above the sea. This summit is a cup-shaped depression, about half a mile in diameter, volcanic rocks towering round it. The depth of this crater does not appear to exceed 30 or 40 feet, and there is no difficulty in walking across it in any direction. The floor of the crater consists of a light white sandy material mixed at places with crystals of sulphur, while rocks crop out here and there. There was a great difficulty in finding a spot sheltered from the sun where I could place my balance and sit down to breathe through the tube. At last some shade was obtained for the balance by means of a blanket, and we managed to creep into a narrow place between two rocks, where the sun's rays could not penetrate. The heat was intense, the sun pouring down upon the Peak from a perfectly clear sky, and everything being nearly too hot to be touched, notwithstanding the intense terrestrial radiation at that altitude. Apparently every circumstance combined to baffle my experiments; the balance would not remain in a horizontal position; a light breeze kept blowing the fine sand about, and I had constantly to remove the beam of the balance to wipe the points of suspension ; then the blanket would not keep in its required position; and I had to lay down at full length on the hot sand without any shelter from the sun to get through the weighings.

* Calculated from Glaisher's Hygrometrical Tables.

The few experiments I succeeded in completing at that spot, showed an evaporation of water from the lungs above that expired at the seaside, equal to 0.141 grm. per minute, or 43.5 per cent.

If the weight of moisture expired at the three principal stations be considered together with the altitudes of the stations, a certain relation will be found to exist between them; this relation is established in the following table, showing what the proportions of humidity expired would amount to if calculated with reference to the barometrical pressures. These figures are entered in the column of the

following table headed Theory.

The results obtained show, therefore, that the evaporation of moisture from the lungs increases as the barometer falls. The ratio is, however, no more than approximate. I question whether a similar result would be obtained in the Alps, where the cold at certain heights must exert a considerable influence on the evaporation from the lungs and air passages.

Results from the Investigation.

The results I have obtained from my experiments on the Island of Teneriffe may be expressed as follows:

:

1. The mean of the whole amount of the carbonic acid expired at the three stations (the experiments at the foot of cone not included) in the sitting posture, and determined from 60 experiments in my case and 55 in that of the guide, was proportional to the weights of our bodies respectively, and amounted to 676 mgms. per 100 kilos. for each of us.

2. The mean weight of the whole carbonic acid expired at the three stations while engaged with the same amount of measured muscular work, and determined from 18 experiments for each of us, was respectively proportional to the weights of our bodies.

3. The mean weight of carbonic acid expired by both of us (with one exception only) was highest during the first or second hour after a meal, while it diminished by degrees as time elapsed since food was taken. This agrees with my results obtained in the Alps.

4. The mean weight of carbonic acid expired by myself on the