B L A 



ftone ; but after the two pipes were added, the weight cf 

 iron-ftone, to produce an equal quahty of iron, was reduced 

 to 2 1, and afterwards to 2v ; producing in the firft inftance 

 per charge 1 1 cwt. of iron upon an average, but latterly not 

 above i cwt. and lolb. of i-on of equal qualities. Another 

 obfervation, in the fame cafe, with every attention paid as 

 to, velocity, quantity, and temperature of air, may be ad- 

 duced as of equil importance, though fomewhat different in 

 its mode of application. 



Under a prclfure ot 2 lbs. a 3 J pipe was found upon the 

 average of 18 weeks to manufafture 20 : 12:0:0 tons ; a 

 3! inch pipe, 20 : 5. Upon an average of 11 weeks, and 

 a 4t pipe, 22:5:. Their refpeftive areas, and iron pro- 

 duced, will ilaud in oppofition thus : 



3I pipe, area 10.6625 quantity of metal 20.12 



l\ . . 12.25 - - - 20.5 



4J - » 18.0625 - - . 22.17 



It is but fair to ftate that the effects of combuftion, fo 



far as it related to the reduction of a quantity of fuel, was not 



in the fame unequal proportion as the quantity of metal to 



the meafure of the air. The quantity of reduftion was 



with the 3 J pipe equarto 25 



3+ - - 31 

 . 4i - - 38 

 But the capacity of the fuel to carbonate the original quan- 

 tity of iron, diminifhed in nearly the fame ratio as the corn- 

 bullion increafed ; fo that the fame meafure by weight which 

 carbonated 140 lbs. of iron with the 3I pipe, was unable to 

 carbonate more than from 96 to 100 lb. of the fame quality 

 with the 4J pipe. This obfervation was made previous to 

 the one laft mentioned, and reafoning upon the fubjeft ltd 

 to the praftice detailed in that experiment. It will appear 

 therefore conclufive, that the fame body of blafl may, with 

 greater advantage and economy, be introduced through 

 two pipes than through one, and this for two reafons. The 

 reduftion is equal, and the quantity of fuel reduced, fmelts 

 and carbonates a larger portion of metal per charge ; but it 

 wiU appear from both cafes equally conclufive, that the capa- 

 city of the fuel to convey carbonation is in the ratio of the 

 fmallnefs of the pipe, or the reduction of the quantity of 

 air. 



This is in unifon with what was dated under the parti- 

 cular " Combuftion ;" that a large volume of air, fo far as 

 it related to the in'.titution of affinity betv^een the coally 

 principle of the fuel, was probably more hurtful to the car- 

 bonation than otherwife ; but that in fo far as it hallened 

 the completion of the affinities, the redudlion of quantity, 

 and above all increafe of produce, though merely as an agent 

 diftroying the fuperfluous fuel, it may be conlidercd as giv- 

 ing the manufatturera fuperiority overhis proccfj by means, 

 the extent of which he never could formerly command. 



Tradition has, though rather imperfeftly, conveyed to us 

 fome fails which our forefathers feemed to have underftood 

 and praflifed with better effeft than their pollerity. In ope- 

 rating with charcoal furnaces, and a blaft proportioned to the 

 fcaniy means then in ufe for the purpofe of producing forge 

 pigs, the whole air was conveyed into the furnace by means 

 of a pipe 2, or at moil 2! inches diameter; but when grey 

 tnttal was wanted, the fame body of air was divided and in- 

 troduced by two pipes, whofe joint capacity was equal to 

 the former. 



It appears therefore an enquiry of fome importance to thofe 

 embarked in iron founderies, to afcertain how far tins tendency 

 of the fuel to increafe the carbonaceous principle proceeds in 

 the ratio of the diminution of the blowpipe. If general ob- 

 fervation confirmed the particulars here ftated, the effefts of 



B L A 



carbonation might be greatly increafed, and the quantity 

 perhaps little reduced, by introducing the fame quan- 

 tity of air by means of four, fix, or eight fmall pipes, 

 whofe conjoint areas lliould be equal to the original column 

 of blall. 



5. From quantity and denfity of air, there may and do 

 refult peculiar properties of blall, which may affect the ope- 

 rations of the furnace, and which once fully underftood may 

 help to explain the fafts hitherto unaccounted for, and 

 which we before noticed. Fafts refulting from accurate ob- 

 fervation would prove an invaluable fource of information 

 upon this fubjedl ; and it is with regret that we can furnilh 

 no perfeft aerological table of the different temperatures of 

 air under different denfitles or degrees of compreffion. The 

 following, we believe, contains the only coUeilion of tem- 

 peratures hitherto noted ; and as it relates to only one degrea 

 of compreffion, the fatisfadlion it affords mull be only 

 partial. 



TABLE of 30 obfervations made in fummer upon various 

 temperatures of air before and during the acl of com- 

 preffion, compared with the thermometer in the (hade. 

 The air thus afcertained, was received into a maga- 

 zine containing 2500 cubical feet, free from moillure 

 or damp entirely. 



Tabaf 



