496

Origin of obtaining a Vacuum by Currents of Steam. [Book V.

draw the vapor arising from a surface of seven square feet. It would bean advantage to apply two or perhaps three separate blowing tubes, ofdifferent sizes, to each sugar pan—using the largest first, to draw off thethe bulk of the vapor, and finishing with the smaller ones. There wouldbe a saving of steam, and the vacuum might be carried higher towardsthe close of an Operation with a very small tube and current.

Another mode of using these tubes to promote evaporation, is to drawair through liquids instead of forcing it through them with pumps, as inthe pneumatic processes of concentrating sirups. An open boiler, four feetin diameter, was inverted and placed in another over a fire and containingsirup : a blowing tube, the orifice of whose vacuum pipe was three-fourthsof an inch diameter, was connected to the inverted vessel, and it drew somuch air under the edges as to cool the liquid to such a degree that theOperation of concentration was prolonged to twice the ordinary time.

While engaged in making the experiments described in this chapter, (in1835) and stimulated by the conviction that we were the first thus to applycurrents of steam for the purposes of raising water and promoting theevaporation of liquids at low temperatures, &c. we were exceedingly sur-prised to learn that something of the kind had been previously done, orproposed to be done, in France . As we had made preparations to securethe invention by a patent here, and by others in Europe , our experimentswere discontinued with a view to ascertain the particulars of the French plan, that it might be known whether we were traveling on beaten groundor not; but to the present time we have not obtained any specific descrip-tion of it, nor do we know whether it consisted of a jet of steam dischargedthrough the centre of a tube, as in Nos. 208, 210, and as applied to in-crease the draft of chimneys in locomotive carriages, or whether the jetwas directed over the outside of a part or the whole of the end of thevacuum tube—nor have we learnt what degree of rarefaction was obtained.We have therefore concluded to insert the preceding notice of our labors,that since we cannot claim priority in the research, we may be allowedthe credit, if any be due, for our modes of application, and the extent towhich they carried the vacuum and are obviously capable of carrying it,especially by such devices as No. 220.

The whole of the devices, from the blowing tubes described in the lastchapter to the apparatus for boiling sugar in vacuo described in this, withthe exception of the patented plan of raising water by a series of vesselson different levels, originated entirely with ourselves, nor were we in-debted either directly or remotely for so much as a hint in maturing themto any persons or writings whatever; and upon them we have also spentno inconsiderable amount both of time and money. But as we have onseveral occasions shown that new devices, so called, are offen old ones, itis but just that we should mete to ourselves the same measure which wehave given to others. We therefore with pleasure record the fact, that ata meeting of the Paris Academy of Arts and Sciences, held in January,1833, M. Pellatans read a paper on the dynamic effects of a jet of steam,of which a notice (not a description of the plan) was published in an Eng-lish journal, and copied into the Journal of the Franklin Institute for Marchof the same year—vol. x, 2d series, p. 195.

There is also described in the London Mechanics’ Magazine, vol. iii, p.275, an experiment of a current of air from a bellows directed over theorifice of an inverted glass funnel, which was placed in a saucer filled withwater. From this (which we did not see tili recently) the blowing tubesdescribed in the last chapter might, with a little ingenuity, have beendeduced.