A Description of the Apparatus for Making Experiments on the Refractions of Fluids: With a Table of the Specifick Gravities, Angles of Observations, and Ratio of Refractions of Several Fluids. By Mr Fra. Hauksbee, F. R. S.

VI. A Description of the Apparatus for making Experiments on the Refractions of Fluids: With a Table of the Specifick Gravities, Angles of Observations, and Ratio of Refractions of several Fluids. By Mr Fra. Hauksbee, F. R. S. The whole Apparatus is fix'd on a Table, parallel to its Surface. On one and the same Axis is fix'd a Sextant, of a Radius of 4 Feet, and a moving Limb to bear the Object. The Sextant is divided into Degrees and Minutes by a Diagonal, and remains always fixt. The Object, which is plac'd on the moving Limb, is seen parallel with the Table when observ'd through the Prism, and at no Degrees on the Sextant; but when any Transparent Liquid is put into the same, the Object must be elevated till it appears to the Eye: Then observing how many Degrees and Minutes the Index on the Limb cuts on the Sextant, we note it, and call it the Angle of Observation. Thus for different Liquids you have different Elevations of the Object, as you will find by the following Table. The Sight-Slit (if I may call it so) is composed of two pieces of Box Wood, plan'd parallel to one another: These Pieces are separated only by 3 slender Slips of common Cards; and with that Intervention are screw'd down one upon the other, exactly parallel with the Axis of the moving Leg and Sextant. The Prism, thro' which it directs the Sight, is plac'd pretty near it, and consists of an Angle of 44.54, which Angle is fix'd Perpendicular to the Plane of the Table, its its upper side being parallel with the same. The Object is a Piece of white Paper, in form of a Cross, pasted on a black Board, and is fix'd at the end of the moving Limb, which is in length about 7 Feet from the Sight; its Diameter is about $2 \frac{1}{2}$ Inches, which just comprehends the Sight through the Slit; so that when the Object is wholly within view, we conclude the Observation to be exact. With this Apparatus the Experiments are made as well by Candle-light as Day-light, (the Presence of the Sun Beams being no ways necessary) and I think they may be depended on as pretty Accurate. I have taken the Specifick Gravity of the several Liquids, where I could obtain a sufficient quantity, as appears by the Table: So that if any Person should have the Curiosity to repeat these Experiments, he must expect a different Angle of Observation, if the Specifick Gravity agree not with the Table; for sometimes it happens, that Liquids of the same Denomination are not always of an equal goodness, and consequently will have a different Specifick Gravity and Refraction. The Christalline Humour of the Ox Eye I prest into the Angle of the Prism, whereby it received the form of it, and gave the Angle of Observation, as specify'd in the Table. I could not see the common Object thro' it, but was forc'd to make use of a Candle for that purpose; the Flame whereof appeared very broad, at least 5 or 6 Inches, nearly in the form of a Half Moon: But what should occasion such a Change of Figure, I cannot at present determine. Of all the Fluids I have try'd, I find nothing to Refract a Ray of Light less than Water; yet there are several other Liquids which make the same Angle. I observe Oil of Bees-Wax to be the lightest Fluid, and Butter of Antimony per Deliquium to be much the heaviest: The difference of Specifick Gravity between these two Bodies, is as 662 is to 1976, that is, nearly as one to three: And the Ratio of their Refractions but as 10000 is to 6885 Bees-Wax, so is 5941 Antimony to the same Radius; that is, as one to 1.16, or thereabouts. Likewise Oil of Vitriol is in Specifick Gravity to Oil of Sasafras, as 1510 is to 898; yet the Ratio of Refraction of the lightest is most considerable, being in proportion as 10000 is to 6475 Sasafras; so is the same Radius to 7011 Vitriol. Thus I find, that a Body doth not Refract in proportion to its Specifick Gravity, but from some quality peculiar to its self; whether it be from its Inflammability, or from any different Texture, or Figure of its Component Parts; or whatever else it be, I shall, with the Application of these Experiments, submit to this Honourable Society to determine. | Specifick Gravities in comparison with a bulk of Water equal to 820 Grains | Angle of Observation | Ratio of Refraction, as 10000 is to | |---|---|---| | Oil of Sasafras 898 | 16.50 | 7485.3 | | Turpentine 713.5 | 25.25 | 6741.8 | | Bees-Wax 662 | 23.30 | 6885.4 | | Carawayes 752 | 26.13 | 6696.5 | | Oranges 711 | 25.20 | 6741.2 | | Hyssop 769.5 | 25.10 | 6757.6 | | Rosemary 747 | 24.40 | 6794.7 | | Savin 789 | 25.30 | 6730.9 | | Origanum 752 | 25.00 | 6770.2 | | Pennyroyal 783 | 25.30 | 6730.9 | | Mint 780.5 | 26.00 | 6706.4 | | Spike 749 | 24.30 | 6807.3 | | Fennel 798 | 27.10 | 6616.5 | | Juniper 729 | 25.10 | 6757.6 | | Cummin 766.5 | 27.00 | 6627.7 | | Tansy 757.5 | 23.46 | 6865.1 | | Dill 795.5 | 27.40 | 6582.7 | Oil | Item | Value | |-------------------------------|-------| | Oil of Amber | 783 | | Cinnamon | 828 | | Cloves | 827 | | Nutmegs | 759 | | Spirit of Wine | 703.5 | | Hartshorn | 786 | | Vinegar | 824.5 | | Sal Armoniack | 794.5 | | Acids, Spirit of Amber | 825 | | Oil of Vitriol | 1510 | | Spirit of Nitre | 1166 | | Aqua Regis | 987 | | Aqua Fortis | 1157 | | Aqua Regis from Aqua Fortis | 1034 | | Butter of Antimony | 1976 | | Spirit of Raw Silk | 916 | | Spirit of Honey | 716 | | Tinct. of Antimony | 693 | | Jesuits Bark | 720 | | Bals. Tolu | 717 | | Gum Amoniacum | 719 | | Metals | 713 | | Vitreous Humor of an Oxes Eye| | | Christalline Humor of the Ox Eye| | | White of an Hens Egg | 17.40 | | Jelly of Hartshorn | 17.50 | | Human Saliva | 16.50 | | Human Urin | 17.05 | | French Brandy | 18.20 | | Oil of Turpentine strongly ting'd Green, with filings of Brass, no ways alters its Refraction. | | Dd 2 VII. An