18 FKVKH. 



horizontal surface of an inch in width, witli an outer upriglit fiau-,'!' of at K-ust an 

 inch and a half in htit,'l»t. In indir to niaki- all tif,'ht, solder must bi- fr<tly used at 

 the corners of the box. In the space thus formed is cemented, by means of soft 

 rnliber dissolved in benzine, a thirk piece of nii\ idi ani/cd in<iia-rnbl)er. Ipi.n 

 the inner edf,'e of the lid (ti^'. H) is soldered a heavy wire (ti;^. 3, a). Whiii the 

 lid is placid in position, u strip of hard wood is laid over caeli ci\^o antl three or 

 more clamps (fi};. I, x) are tij,'htly screwed down upon it. Ihe w iri' of course buries 

 itsi'lf in the soft rubber, and a perfectly ti;,'ht joint is obtained. 



The lid has in it five holes, two of these ti<^. '.i, c) receive the tubes from the 

 inn«'r box; through a third ix) the stirrer [)rojects, and tiie remainder (y) are fitted 

 with milled screw-caps so that they can be o])ene(l or closed ut will. These are for 

 takin*; the temperature of the water as well as for tiie purpose of tilling and empty- 

 iu" the box; they must be so placed that they are exactly over the space betweeu 

 the inner and the tiuter box, in order to allow the thirmomeler to descend readdy. 

 When water is put into the large box the iinier Ih)X floats u|)ward with great 

 force; to obviate this a pair of projecting jjieccs of-iron (tig. 1, x) are riveted u|)on 

 the inside of the larger box in such a way that when a bar is slipped under them 

 it will hold the smaller box down in position. The stirrer consists of a broad piece 

 of iron the length of the width of the inner box, with an iron rod fastened at right 

 angles to it; the flat part when the apparatus is in working condition lies upon the 

 bottom, and as it can be drawn up and down by the iron rod, it afi'ords an efficient 

 means of producing agitation in the water. 



When the apparatus (tig. 1) is arrfinged for use, the animal is ])laced in the inner 

 b«»x, and between the boxes is a layer of water (w), and surrounding the whole is 

 sawdust, cow's hair, or other non-conductor (s). One of the tubes from the inner 

 box conununicates directly with the open air, the other with a jmmp which draws 

 a current of air through the box and through a gas meter. The air drawn fnmi 

 the box passes around and about a thermometer bulb, so that its temperature is 

 readily taken. If the temperature of the air as it enters and as it leaves the box 

 Im- known, and also its quantity, and if, likewise, the quantity of the water an«l the 

 weight of the iron containing it, and also their temperature when the animal is put 

 in and when it is taken out be ascertained, it is a very simple matter to calculate 

 the amount of heat given off by the animal. 



The calorimeter, as descrilied thus far, makes no provision for estimating the heat 

 lost or gained by vaporization or condensation of moisture within the chamber. In 

 some European instruments this difficulty is avoided by leading the exit tube at 

 some length around through the water which is kept at a low temiurature .so as to 

 ,...,.1....... all the vapor. The objections to this arrangement are to my thinkitig 



In tlie first place, heat may be obtained bv condensation of vapor com- 

 ing in with the external nir, especially as the water should be cooler than the air, 

 for reasons to be mentioned directly; in the second place, the completeness of the 

 ' ' ■ " is always uncertain. \ more accurate plan is foiind iti the analysis, 

 ' '-■<■, of a measured sample of the air h-aviug the box. and also of that 



entering the box, by means of sidplmric acid bulbs or chloride of calcium tubes. 

 In sonic of our experiments the samples drawn off from the main currents of nir 



