It was also perceptible, that the air was impelled somewhat, tho' not considerably, more forward by the addition of each hundred weight on the bellows:

That the deeper the horizontal pipe was placed in the water, the less resistance was made by the steam:

That in proportion as the heat of the steam was increased, by making the water boil more strongly, the resistance to the pressure of the air by the weight on the bellows became greater.

It is a very doubtful matter, whether air forced thro' boiling water would have answered the purpose intended: but I believe it was never imagined, that air could not be readily forced thro', until proved by the foregoing experiments. The attempt, tho' it has failed demonstrably in that point, has produced the same effect from another cause, as to saving coals, and throwing up more water. For, by the constant care, that was taken during the time of making these experiments, to measure the coals, to admit only a proper quantity of fuel to be laid on, and also to mark the time exactly it took in burning; the engine then did, and still continues to require eight bushels of coals less, in every 24 hours work, than it did before; and also, from the regularity of its stroke, to throw up more water; the same care being required from the engineer, who can have no pretence for consuming more coals now, than appeared sufficient during the time the experiments were making.

Tho' some of the properties of steam are well known; yet the degrees of expansion it is capable of; whether air be mixed with, or necessary to, its formation; as also how far its power of resistance may reach; are probably not yet known, to a proper degree of exactness. Niewentit fixes the expansion of a cubical inch of water, converted into steam, at 13365, Dr. Desaguliers at 14000, and Mr. Payne at 4000 times. The great scope in this subject from a plenum to a vacuum, if I may be allowed the expression, as also the very useful purposes, to which it has already been, and possibly may be still further applied, will, I hope, be an inducement to those, who are much better qualified, to proceed in so useful an inquiry.

XLVI. Observatio Eclipsis Lunæ Die 27 Martii, Ann. 1755. habita Ulissipone in Domo Patrum Congregationis Oratorii à Joanne Chevalier ejusdem Congregationis Presbytero, Regiæ Londinensis Societatis Socio, Regiæque Parisiensis Scientiarum Academiæ correspondente.

Tubo optico 8 pedum peracta est observatio cœlo sereno, claroque.

Read Dec. 8, 1757.

Immersiones.Hora postmeridiana temporis veri.
h ' "
Initium penumb rædubium 10 29 50
Initium eclipsis dubium 10 33 35
Certe jam incæperat 10 34 05
Umbra ad mare humorum 10 44 00
Umbra ad Grimaldum 10 44 53
Grimaldus totus in umbra 10 47 58
Mare humorum totum in umbra 10 51 14
Thico incipit mergi 10 53 29
Thico totus mergitur 10 55 14
Umbra ad Reinholdum 11 08 04
Umbram ingreditur Copernicus 11 19 22
Umbra ad mare nectaris 11 24 52
Totum in umbra 11 33 50
Umbra ad mare tranquillitatis 11 35 24
Promontorium acutum in umbra 11 45 46
Emersiones.
h ' "
Incipit emergere ab umbra Copernicus 1204 38
Totus Copernicus extra umbram12 07 40
Incipit egredi Grimaldus 12 09 38
Totus Grimaldus extra umbram 12 12 38
Incipit emergere mare fœcunditatis 12 31 37
Emergit mare humorum 12 36 11
Incipit emergere Capuanus 12 39 40
Egreditur Schicardus 12 48 30
Emergit Thico 12 51 40
Totum mare nectaris egreditur 12 58 09
Finis eclipsis 13 13 02
Finis penumbræ dubius 13 16 50