IRON. 



tfiat tJie excefs of moldure contained in the air in fummer 

 alH)ve that in the winter, might explain the phenomenon. 

 Whatever may be the caiife of this difference in the blaft- 

 furnace, the fame may equally be referred to common fires, 

 which, it is well known to every one, are much hotter in 

 winter than in fummer. If the Lavoifierian docln;;e of 

 ccmbuftion were true, we (hould not expedt that the power 

 of air to generate heat would vary with the temperature, 

 fince the fame caloric which h.id contributed to dilate the 

 oxy,^en in fummer, would be g-iven up when the oxygen 

 combined with the carbon. Unfortunately for that doc- 

 trine, however, we find that the quantity of heat generated 

 during the combination of oxygen, is direftly as the quan- 

 tity of oxygen, whatever may be its Hate, whether fohd, 

 liquid, or aeriform. 



It appears from general obfervation, tliat the difference in 

 th^ quantity and quality of the iron made in winter and 

 fummer inay be, in a great meafure, referred to changes 

 arifing from variation of temperature. The average refult 

 of this atmofpheric influence is different with different blalt- 

 furnacc?, and, indeed, with the materials employed ; but in 

 general the quantity varies in winter and fummer from j th to 

 ith, befides the alteration of quality, which in fome furnaces 

 cannot be prevented by any change in the burthen. 



If the whole of this difference depend upon the tempe- 

 rature cf the blaft fent into the furnace, we muft expedl to 

 find it either in the increafed rarity of the air, or in the pre- 

 fence of moifture, which exifts more abundantly in the atmo- 

 fphere in fummer than in winter ; or, perhaps, it may be 

 attributab'e to both thefe circumftances. 



Soon after the conftituent parts of water were difcovered, 

 fome iron-mafters attempted to produce combuftion by blow- 

 ing fteam into the furnace. But, notwithflanding the great 

 proportion of oxygen exifting in aqueous vapour, their ex- 

 peftations were far from being realized, and the fcheme was 

 given up by them under a firm conviction that it never could 

 fucceed. 



Tliis experiment, however, fervcd to {hew that no more 

 mifchief might be expetted from the vapour of wa'.er in the 

 atmofphere, than its merely excluding a portion of oxygen. 

 Conceiving it, therefore, to have no other influence in the 

 furnace, we will fubmit fome calculations to the reader, in 

 order to flijw the abfohile difference in the quantity of 

 oxygen fent into the furnace in winter and in fummer, and 

 to afcertain what fiiarc of the defeft may be attributed to 

 this circumftance, or whether the whole may not fafely be 

 referred to it. 



We have much to regret that we are not in poffefiion of 

 more experiments as to the temperature of the air fent into 

 the furnace at different times of tlic year. The mere tem- 

 perature of the atmofphere is not fuiBcient for this purpofe, 

 frncc the air gives out much heat by compreffion in the blow- 

 ing cylinder. In a former part of this work, (fee Bl.\st- 

 furnace), a table of fome obfervations was given, on 

 which, as far as they go, reliance may confidently be placed. 

 In this table the temperature of the air was Hated when it 

 tnlered the blo-ving cylinder, and after it had been com- 

 preffed into a vault, from which it paffed into the furnace. 

 If we take the temperature on its entrance into the furnace 

 in winter at 50 , and in fummer at 100", the difference will 

 be 50', and the variation in the quantity of oxygen will be 

 inverfely as the increafed volume of the air. It is found 

 that elallic fluids are augmented in bulk by one degree of 

 Fahrenheit .00208 of the whole. Therefore, the quantity 

 cf ojcygen at 50' will be to that at 100^ as i 4- (100 — 



50) X .00208 : I ; and the oxygen, confequently, i.. 

 fummer will be .104, or little more than .j^-.th lefs than i;j 

 winter. 



The defeft arifing from the relative quantities of moif- 

 ture contained in the air in winter and fummer will be very 

 tripling, except where the water-regulator is employed 

 inilead of the air vault or common regulator. (See Blast - 

 furnace.) When the air does not come in contact wit!- 

 any thing moift after entering the blowing cylinder, in order 

 to learn the quantity of water prefent, we have only to 

 afcertain the relative proportions of vapour- esi.'Hng at the 

 refpective temperatures of the atmofphere in winter and 

 fpmmer. It appears from a theorem, which we have founded 

 upon Mr. Daiton's ingenious experiments upon evaporation 

 and the force of vapours, tliat the quantity of water in 

 air at 32^ at which temperature we fuppofe it to enter the 

 furnace in winter, is equal to 2.04 grains in each cubic 



foot. This, in weight, is ^^^' ; and in bulk, vapour being 



to air at 32^ as 274 to ^( 



eqv 



d to 



.04 



of the whole. 



or .0075'. '^'1'^ fummer air, which we take at ^^'', con- 

 tains 5.32 grains in a cubic foot; a quantity amounting in 



weight to i^, and in bulk to-—, or .019 of the 

 524 274 ^ 



whole. The difference .01 1 J is the deficiency of common 

 air in fummer, arifing from the prefence of aqueous vapour ; 

 and makes the total variation in the quantity of oxygen be- 

 tween fummer and winter equal to .llf C = — ^ , or ^tli 

 ^ ■'-' 200' * 



nearly. 



We here confider water as producing injury merely bj 

 difplacing a certain proportion of oxygen, and not being 

 prejudicial in itfelf, as is fuppofed by the generality of iron- 

 mafters. The reafon given for its bad effects does not ap- 

 pear intitled to much weight. The opinion commonly 

 entertained is, that the carburetted hydrogen fet at liberty, 

 carries off a greater quantity of heat than the nitrogen of 

 atmofpheric air. An effeft which, if even true, is inade- 

 quate to explain the appearances. When the air is received 

 into a water-regulator, as is the cafe in many blafl-fumace 

 works, a much larger quantity of moifture may be expefled 

 to enter the furnace, than with the ordinari- apparatus. In 

 the above calculation, if the air had been received over wa- 

 ter, we fl'iou'd find that its temperature in the receiving 

 veffel in winter and funim.er would be jo and 100". The 

 vapour in the former amounts to 4.67 grains in a cubic foot : 

 in the latter, to iS.gj grains in the fame quantity. 



Hence, air at 100' will contain lefs oxygen than that at 

 50 , by .05 J of the whole; which is a little more than 

 ,',th. This added to the lofs by increafed temperature 

 alone, will be .IJ9, or nearly 15th. 



We may from this conclude, that the extra-quantity of 

 moillure admitted by ufing the water-regulator, will at any 

 rate increafe the difference in the amount of oxygen from 

 -gth to gth, or thereabouts ; which, in all probability, will 

 more than counter-balance the good effefts arifing from its 

 uniform preffure. There does not appear to be, in the 

 prefent ftatc of our knowledge, any means of effeftually 

 remedying this evil. Some good might accrue from ad- 

 mitting the exterior air as cold as poflible, and rot allowing 

 it to come in contaifl with water after entering the blowing- 

 cylinder. This may be done to a certain degree, by caufing 

 5t the 



