Electricity and magnetism touch in some points upon heat. Heat produces electrical currents; electrical currents produce heat. Heat destroys magnetism. Melted iron is incapable of magnetic influence. Reduction of temperature in iron so far decreases the force, that a celebrated philosopher made an elaborate series of experiments to ascertain whether a great reduction of temperature might not develop magnetic properties in metals other than iron. This branch of thermo-electricity has received from us but little attention. Franklin's experiments, by placing differently colored cloths in the snow, and showing the depth to which they sank, are still quoted, and great praise has been bestowed abroad on a more elaborate series of experiments, by a descendant of his, Dr. A. D. Bache, proving that this law does not hold good as to heat, unaccompanied by light. The experiments of Saxon and Goddard demonstrate that solid bodies do slowly evaporate. It is proper here to mention our countryman, Count Rumford, whose discoveries as to the nature and properties of heat, improvement in stoves and gunnery, and in the structure of chimneys and economy of fuel, have been so great and useful.
Light accompanies heat of a certain temperature. That it acts directly to increase or decrease magnetic force, is not yet proved; and the interesting experiments made by Dr. Draper, in Virginia, go to show that it is without magnetic influence. The discussion of this subject forms, the branch of optics, touching physical science on the one side, the most refined, and the highest range of mathematics on the other. Rittenhouse first suggested the true explanation of the experiment, of the apparent conversion of a cameo into an intaglio, when viewed through a compound microscope, and anticipated many years Brewster's theory. Hopkinson wrote well on the experiment made by looking at a street lamp through a slight texture of silk. Joscelyn, of New York, investigated the causes of the irradiation manifested by luminous bodies, as for instance the stars. Of late, photographic experiments have occupied much attention, and Draper has advanced the bold idea, supported by experiment, that the agent in the so-called photography, is not light, nor heat, but an agent differing from any other known principle. Henry has investigated the luminous emanation from lime, calcined with sulphur, and certain other substances, and finds that it differs much from light in some of its qualities.
Astronomy is the most ancient and highest branch of physics. One of our earliest and greatest efforts in this branch was the invention of the mariner's quadrant, by Godfrey, a glazier of Philadelphia. The transit of Venus, in the last century, called forth the researches of Rittenhouse, Owen, Biddle, and President Smith, near Philadelphia, and of Winthrop, at Boston. Two orreries were made by Rittenhouse, as also a machine for predicting eclipses. Most useful observations, connected with the solar eclipses, from 1832 to 1840, have been made by Paine, of Boston. We have now well-supplied observatories at West Point, Washington, Cambridge, Philadelphia, Hudson, Ohio, and Tuskaloosa, Alabama; and the valuable labors of Loomis, Bartlett, Gillis, Bond, Pierce, Walker, and Kendall are well known. Mr. Adams, so distinguished in this branch and that of weights and measures, laid last year the corner stone of an observatory at Cincinnati, where will soon be one of the largest and most powerful telescopes in the world. Most interesting observations as to the great comet of 1843 were made by Alexander, Anderson, Bartlett, Kendall, Pierce, Walker, Downes, and Loomis, and valuable astronomical instruments have been constructed by Amasa Holcomb, of Massachusetts, and Wm. J. Young, of Philadelphia.
It is difficult to class the brilliant meteors of November the 13th, 1833. If such meteors are periodic, the discovery was made by Professor Olmsted; and Mr. Herrick, of New Haven, has added valuable suggestions. The idea that observers, differently placed at the time of appearance and disappearance of the same meteor, would give the means of determining differences of longitude, was first applied in our own country, where the difference of longitude of Princeton and Philadelphia was determined by observations of Henry and Alexander, Espy and Bache. In meteorology our countrymen have succeeded well. Dr. Wells, of South Carolina, elaborated his beautiful and original theory of the formation of dew, and supported it by many well-devised and conclusive experiments. The series of hourly observations, by Professor Snell and Captain Mordecai, are well known; and the efforts of New York and Pennsylvania, of the medical department of the army, and its present enlightened head, Dr. Lawson, have much advanced this branch of science. The interesting question, Does our climate change? seems to be answered thus far in the negative, by registers kept in Massachusetts and New York. There are two rival theories of storms. That of Redfield, of a rotary motion of a wide column of air, combined with a progressive motion in a curved line. Espy builds on the law of physics, examines the action of an upmoving column of air, shows the causes of its motion and the results, and then deduces his most beautiful theory of rain and of land and water spouts. This he puts to the test of observation; and in the inward motion of wind toward the centre of storms, finds a striking verification of his theory. This theory is also sustained by the overthrow or injury, in the recent tornado at Natchez, of the houses whose doors and windows were closed, while those which were open mostly escaped unhurt. Mr. Espy must be considered, not only here, but throughout the world, as at the head of this branch of science. This subject has been greatly advanced by Professor Loomis, whose paper has been pronounced, by the highest authority, to be the best specimen of inductive reasoning which meteorology has produced. The most recent and highly valuable meteorological works of Dr. Samuel Forry are much esteemed. Many important discoveries in pneumatics were made by Dr. Franklin and Count Rumford, and the air pump was also greatly improved by Dr. Prince, of Salem.
Chemistry, in all its departments, has been successfully pursued among us. Dana, Draper, Ellet, Emmet, Hare, the Mitchells, Silliman, and Torrey, are well known as chemical philosophers; and Booth, Boyé, Chilton, Keating, Mather, R. Rogers, Seybert, Shepherd, and Vanuxen, as analysts; and F. Bache, Webster, Greene, Mitchell, Silliman, and Hare, as authors. In my native town of Northumberland, Pennsylvania, resided two adopted citizens, most eminent as chemists and philosophers, Priestley and Cooper. The latter, who was one of my own preceptors, was greatly distinguished as a writer, scholar, jurist, and physician, as well as a chemist. Priestley, although I do not concur in his peculiar views of theology, was certainly one of the most able and learned of ecclesiastical writers, and possessed also a mind most vigorous and original. His discoveries in pneumatic chemistry have exceeded those of any other philosopher. He discovered vital air, many new acids, chemical substances, paints, and dyes. He separated nitrous and oxygenous airs, and first exhibited acids and alkalies in a gaseous form. He ascertained that air could be purified by the process of vegetation, and that light evolved pure air from vegetables. He detected the powerful action of oxygenous air upon the blood, and first pointed out the true theory of respiration. The eudiometer, a most curious instrument for fixing the purity of air, by measuring the proportion of oxygen, was discovered by Dr. Priestley. He lived and died in my native town, universally beloved as a man, and greatly admired as a philosopher. Chemistry has actively advanced among us during the present century. Hare's compound blowpipe came from his hand so perfect, in 1802, that all succeeding attempts of Dr. Clark, of England, and of all others, in Europe and America, to improve upon it or go beyond the effects produced, have wholly failed. His mode of mixing oxygen and hydrogen gases, the instant before burning them, was at once simple, effective, and safe. The most refractory metallic and mineral substances yielded to the intense heat produced by the flame of the blowpipe. In chemical analysis, the useful labors of Keating, Vanuxen, Seybert, Booth, Clemson, Litton, and Moss, would fill many volumes. In organic chemistry, the researches of Clark, Hare, and Boyé were rewarded by the discovery of a new ether, the most explosive compound known to man. Mitchell's experiments on the penetration of membranes by gases, and the ingenious extension of them by Dr. Rogers, are worthy of all praise. The softening of indiarubber, by Dr. Mitchell, renders it a most useful article. Dyer's discovery of soda ash yielded him a competence. Our countrymen have also made most valuable improvements in refining sugar, in the manufacture of lard oil and stearin candles, and the preservation of timber by Earle's process. Sugar and molasses have been extracted in our country from the cornstalk, but with what, if any profit, as to either, is not yet determined. No part of mechanics has produced such surprising results as the steam engine, and our countrymen have been among the foremost and most distinguished in this great and progressive branch. When Rumsey, of Pennsylvania, made a steamboat, which moved against the current of the James River four miles an hour, his achievement was so much in advance of the age, as to acquire no public confidence. When John Fitch's boat stemmed the current of the Delaware, contending successfully with sail boats, it was called, in derision, the scheme boat. So the New Yorkers, when the steamboat of their own truly great mechanic, Stevens, after making a trip from Hoboken, burnt accidentally one of its boiler tubes, it was proclaimed a failure. Fulton also encountered unbounded ridicule and opposition, as he advanced to confer the greatest benefits on mankind by the application of steam to navigation. So Oliver Evans, of Pennsylvania (who has made such useful improvements in the flour mill), was pronounced insane, when he applied to the Legislatures of Pennsylvania and Maryland for special privileges in regard to the application of steam to locomotion on common roads. In 1810 he was escorted by a mob of boys, when his amphibolas was moved on wheels by steam more than a mile through the streets of Philadelphia to the river Schuylkill, and there, taking to the water, was paddled by steam to the wharves of the Delaware, where it was to work as a dredging machine. Fulton's was the first successful steamboat, Stevens's the first that navigated the ocean, Oliver Evans's the first high-pressure engine applied to steam navigation. Stevens's boat, by an accident, did not precede Fulton's, and Stevens's engine was wholly American, and constructed entirely by himself, and his propeller resembled much that now introduced by Ericsson. Stevens united the highest mechanical skill with a bold, original, inventive genius. His sons (especially Mr. Robert L. Stevens, of New York) have inherited much of the extraordinary skill and talent of their distinguished father. The first steamboat that ever crossed the ocean was built by one of our countrymen, and their skill in naval architecture has been put in requisition by the Emperor of Russia and the Sultan of Turkey. The steam machines invented by our countrymen to drive piles, load vessels, and excavate roads, are most ingenious and useful. The use of steam, as a locomotive power, upon the water and the land, is admirably adapted to our mighty rivers and extended territory. From Washington to the mouth of the Oregon is but one half,[3] and to the mouth of the Del Norte but one fourth, of the distance of the railroads already constructed here; and to the latter point, at the rate of motion (thirty miles an hour) now in daily use abroad, the trip would be performed in two days, and to the former in four days. Thus, steam, if we measure distance by the time in which it is traversed, renders our whole Union, with its most extended limits, smaller than was the State of New York ten years since. Steam cars have been moved, as an experiment, both here and abroad, many hundred miles, at the rate of sixty miles an hour; but what will be the highest velocity ultimately attained in common use, either upon the water or the land, is a most important problem, as yet entirely unsolved. Our respected citizens, Morey and Drake, have endeavored to substitute the force of explosion of gaseous compounds for steam. The first was the pioneer, and the second has shown that the problem is still worth pursuing to solution. An energetic Western mechanic made a bold but unsuccessful effort to put in operation an engine acting by the expansion of air by heat; and a similar most ingenious attempt was made by Mr. Walter Byrnes, of Concordia, Louisiana; as also to substitute compressed air, and air compressed and expanded, as a locomotive power. All attempts to use air as a motive power, except the balloon, the sail vessel, the air gun, and the windmill, have thus far failed; but what inventive genius may yet accomplish in this respect, remains yet undetermined. There is, it is true, a mile or more of pneumatic railway used between Dublin and Kingstown. An air pump, driven by steam, exhausts the air from a cylinder in which a piston moves; this cylinder is laid the whole length of the road, and the piston is connected to a car above, so that, as the piston moves forward on the exhaustion of the air in front of it, the car is also carried forward. The original idea of this pneumatic railway was derived from the contrivance of an American, quite unknown to fame, who, as his sign expressed it, showed to visitors a new mode of carrying the mail,[4] more simple, and quite as valuable, practically, as this atmospheric railway. The submerged propeller of Ericsson, and the submerged paddle wheel, the rival experiments of our two distinguished naval officers, Stockton and Hunter, are now candidates for public favor; and the Princeton on the ocean, as she moves in noiseless majesty, at a speed never before attained at sea, seems to attest the value of one of these experiments, while the other is yet to be determined. The impenetrable iron steam vessel of Mr. Stevens is not yet completed, nor have those terrific engines of war, his explosive shells, yet been brought to the test of actual conflict.
In curious and useful mechanical inventions, our countrymen are unsurpassed, and a visit to our new and beautiful Patent Office will convince the close observer that the inventive genius of America never was more active than at the present moment. The machines for working up cotton, hemp, and wool, from their most crude state to the finest and most useful fabrics, have all been improved among us. The cotton gin of Eli Whitney has altered the destinies of one third of our country, and doubled the exports of the Union. The ingenious improvements for imitating medals, by parallel lines upon a plain surface, which, by the distances between them, give all the effects of light and shade that belong to a raised or depressed surface, invented by Gobrecht and perfected by Spencer, has been rendered entirely automatic by Saxton, so that it not only rules its lines at proper distances and of suitable lengths, but when its work is done it stops. In hydraulics, we have succeeded well; and the great aqueduct over the Potomac at Georgetown, constructed by Major Turnbull, of the Topographical Corps, exhibits new contrivances, in overcoming obstacles never heretofore encountered in similar projects, and has been pronounced in Europe one of the most skilful works of the age.
The abstract mathematics does not seem so well suited to the genius of our countrymen as its application to other sciences. Those among us who have most successfully pursued the pure mathematics, are chiefly our much-esteemed adopted citizens, such as Nulty, Adrain, Bonnycastle, Gill, and Hassler. Bowditch was an American, and is highly distinguished at home and abroad. Such men as Plana and Babbage rank him among the first class, and his commentary on the 'Mécanique Céleste' of Laplace, has secured for him a niche in the temple of fame, near to that of its illustrious author. Anderson and Strong are known to all who love mathematics, and Fischer was cut off by death in the commencement of a bright career. And may I here be indulged in grateful remembrance of two of my own preceptors, Dr. R. M. Patterson and Eugene Nulty. The first was the professor at my Alma Mater (the University of Pennsylvania) in natural philosophy and the application of mathematics to many branches of science. He was beloved and respected by all the class, as the courteous gentleman and the profound scholar; and the Mint of the United States, now under his direction, at Philadelphia, has reached the highest point of system, skill, and efficiency. In the pure mathematics Nulty is unsurpassed at home or abroad. In an earlier day, the elder Patterson, Ellicot, and Mansfield cultivated this branch successfully in connection with astronomy.
A new and extensive country is the great field for descriptive natural history. The beasts, birds, fishes, reptiles, insects, shells, plants, stones, and rocks are to be examined individually and classed; many new varieties and species are found, and even new genera may occur. The learned Mitchell, of New York, delighted in these branches. The eminent Harlan, of Philadelphia, and McMultrie were of a later and more philosophic school. Nuttall, of Cambridge, has distinguished himself in natural history, and Haldeman is rising to eminence.
Ornithology is one of the most attractive branches of natural history. Wilson was the pioneer; Ord, his biographer, followed, and his friend Titian Peale; Audubon is universally known, and stands preëminent; and the learned Nuttall and excellent and enthusiastic Townsend are much respected. Most of these men have compassed sea and land, and encountered many perils and hardships to find their specimens. They have explored the mountains of the North, the swamps of Florida, the prairies of the West, and accompanied the Exploring Expedition to the Antarctic, and round the world. As botanists, the Bartrams, Barton, and Collins, of Philadelphia, Torrey, of New York, Gray and Nuttall of Cambridge, Darlington, of Westchester, are much esteemed. The first botanical garden in our country was that of the Bartons, near Philadelphia; and the first work on botany was from Barton, of the same city. Logan, Woodward, Brailsford, Shelby, Cooper, Horsfield, Colden, Clayton, Muhlenburg, Marshall, Cutler, and Hosack, were also distinguished in this delightful branch.
A study of the shells of our country has raised to eminence the names of Barnes, Conrad, Lea, and Raffinesque. The magnificent fresh-water shells of our Western rivers are unrivalled in the Old World in size and beauty. How interesting would be a collection of all the specimens which the organic kingdom of America presents, properly classified and arranged according to the regions and States whence they were brought! Paris has the museum of the natural history of France, and London of Great Britain; but Washington has no museum[5] of the United States, though so much richer in all these specimens.