And did not Dr. HALLEY, so long the ornament of this society, communicate in the year 1686 a Paper, which he calls _A discourse concerning gravity_, in which, treating of the motion of projectiles, he says, that being aware of the deflexion from the parabolic curve that might be occasioned by the resistance of the air, he had made some experiments, even with cannon-balls, to estimate the force of that resistance; yet conclude, _That in large shot of metal, whose weight many thousand times surpassed that of air, and whose force is very great, in proportion to the surface wherewith they press thereupon, this opposition was not discernible_. And again, _Though in small and light shot, the opposition of the air ought and must be accounted for; yet in shooting great and weighty bombs, there need be very tittle allowance made; and so these rules_ [those, to wit, grounded on the principle of GALILEO] _may be put in practice to all intents and purposes, as if this impediment_ [the resistance of the air] _were absolutely removed_[14]. Such conclusions, which we now find to be erroneous, were the less to be expected from so eminent a person, as they argued too much haste to finish a theory, that was to be made subservient to present use. It might indeed have been expected, that men of science applying themselves to this study, would have been sooner awakened to the consideration of the great opposition of the air, by the _Principia_ of NEWTON, published a little after this Paper of HALLEY’s[15]. For in that excellent work the illustrious author had demonstrated, that the curve described by a projectile, in a strongly resisting medium, differed much from a parabola, and that the resistance of the air was great enough to make the difference between the curve of projection of heavy bodies and a parabola far from being insensible, and therefore too considerable to be neglected. Have we not then less to plead for not attending to the _Principia_ of NEWTON in this article[16], than the mathematicians of other nations, who, as M. de FONTENELLE observes[17], partly from the difficulty of understanding that concise and profound work, and partly from a misapprehension of its tendency (which they fancied was to revive the exploded doctrine of _occult qualities_) were late in becoming acquainted with it? But it is not so easy to account for their inattention to HUYGENS, a known and even then a much esteemed author, and who indeed was second to NEWTON alone in science and in genius. For he in the year 1690 had published a treatise on _Gravity_, written in a popular manner, wherein he gave an account of some experiments he had made at Paris, and in the academy, by which, as well as by mathematical investigations, he was convinced of the truth of NEWTON’s conclusions, in regard to the great opposition of the air to bodies moving swiftly in it; and, by consequence, believed that the track of all projectiles was very different from the line of a parabola[18].