b. November 8, 1656 and d. January 14, 1742

English astronomer. He invented means of observing eclipses, improved the sextant, and on November 7, 1677, made the first complete observation of a transit of Mercury. He demonstrated in 1686 the relation of elevation to the density of the atmosphere and applied it to barometric readings; he materially improved diving apparatus, experimented on the dilation of liquids by heat, and by his scientific voyages laid the foundation of physical geography. His discovery of the long inequality of Jupiter and Saturn; of the acceleration of the mean motion of the moon; his prediction of the return of the comet which bears his name; his researches in terrestrial magnetism; his suggestions regarding the determination of the sun’s parallax, and his meteorological, mathematical, optical and statistical researches evince a universality of talent of rare occurrence.

And many a point, at distance dimly view’d,
For idle loiterers and unmeasured height,
By persevering energy subdued,
Rewards the bold adventurer with a sight
Of undiscover’d worlds-vast regions of delight.

—The Pursuit of Learning: John Herman Merivale

1610—Jupiter’s satellites were discovered.

b. ? 1778 and d. ? 1848

French engineer and optician. He produced a mechanical barometer and made areometers of great perfection. He gave to the public the double opera glasses, produced the isocentric glasses, invented numerous eye-glasses, a new pancreatic microscope and an alembic for testing the quality of wine; he also invented the optic scale.

Who formed the curious organ of the eye,
And cloth’d it with its various tunicles,
Of texture exquisite; with crystal juice
Supplied it, to transmit the rays of light;
Then plac’d it in its station eminent,
Well fenc’d and guarded, as a sentinel
To watch abroad, and needful caution give?

—Needler

1370—Spectacles were invented.

1500—Leonardo da Vinci noticed the difference of vision with each eye, and Francis Aquilonius, in 1613, made it the subject of a treatise.

1640—Athanasius Kircher invented the magic lantern.

1807—Dr. Wollaston invented a camera lucida.

1838—The first factory in the United States for making gold spectacles and silver thimbles was started at Long Meadow, Mass.

1851—Helmholtz invented the ophthalmoscope, an apparatus for inspecting the interior of the eye.