j4 ContbuflnH entited hy htated OifygtH. 



affords a degree of conTcnience, equally obvious, with regard to the putting in, placing, 

 and taking out the vefFels. Of the refrigeratory, the receiver I, and the apparatus M h, 

 little more need be faid than that they are conftruflred in the forms which experience has 

 fiiewn to be the mofl fimple and efficacious. The parts NOP exhibit an improvement 

 which is found to be of great importance. Mr. Sadler obferved, in the courfe of his experi*- 

 ments, that the efie£t of the oxygen, when recently produced, was much greater than fome 

 hours afterwards. There was no reafon to conclude that this difference arofe from any 

 change in the purity of the fluid : he therefore concluded that it muft be caufed by a 

 difference of temperature. When the cold oxygen is brought into contacH: with a com- 

 buftible body at a very elevated temperaturt-, it muft be concluded, that part of the caloric 

 difengaged at the inftant of combination muft be employed in raifing the temperature of 

 the mafs of oxygen, and confequcntly that the intenfity of the combuftion will be lefs. 

 He therefore determined to fupply this portion of caloric from another procefs of com- 

 buftion, carried on near the external furface of the tube through which the oxygen is tranf- 

 mitted. O is the lamp for that purpofe, affi^rding a flame, which heats the tube N, and 

 gives an elevated temperature to the oxygen before it palTes out of the fmall aperture P. 

 The heat excited in a piece of charcoal urged by this ftream of oxygen is fo great, as to 

 fufe the pureft fpecimens of native rock cryftal, and alfo thofe of lime. The other eff^edli 

 are llkewife proportionally greater. 



Ohfervations on the Common Bloiu-P'tpe. 



CHEMISTS and mineralogifts are too well acquainted with the ufe of this inftrument, to 

 require any long enumeration of its advantages. To behold with eafe fuch proceffes as demand 

 much labour and time in furnaces, and cannot in this laft fituation be eaiily and comfortably 

 infpefted ; — to fee thefe performed in the open air in a few feconds, with all the changes 

 of colour,; ebullition, fcoriation, and the like ; — to remark the nature of the vapours which 

 fly off, and to note the precipitation of metallic fubftances from their fluxes, or the effefts 

 they produce on the feveral kinds of glafs : — thefe are a few of the advantages which have 

 brought this inftrument into eftimation. 



It is well known that the common praftice of blowing with the mouth, though very 

 leady, and requiring an inftrument of inconfiderable coft, is not fo advantageous as the ex- 

 trufion of air by means of bellows, or other mechanical contrivances. The air exhaled 

 from the lungs has already been deprived of part of its oxygen, and is loaded with humi- 

 dity. The procefs of blowing, even to the moft fkilful, is attended with fome fatigue, and 

 requires a degree of confinement of the head and one of the hands, which confiderably di- 

 minifhes the power, as well as the eafe of the operator. Bellows, at the price of two and 

 three guineas the fet with a few additional implements, have been contrived for this 

 purpofe. It fecmed probable to me, that thefe inftruments are larger and more coftly 

 than is requiiite. To afcertain the value of this fufpicion, I made the following expe- 

 riments : 



A blow-pipe nearly of the figure defcribed by Bergmann, whofe internal diameter was 

 about one fifth of an inch at the fmallcft part, was inferted through the cork of a bottle, 

 of which the contents were 17^ cubic inches^ The cork was notched ^ fuch a manner 



diat 



