*GEOLOGY.

   The rock underlying the soil or drift deposit of Clinton County is the Niagara limestone. In some earlier geological epoch, it was either deposited at a uniform level with the surface of the sea, or the water receded from it, leaving it dry. It was never greatly disturbed by earthquakes or upheavals, so that it now remains in nearly horizontal strata. Its chemical composition is a carbonate of lime and magnesia, with a small amount of silica and alumina, colored yellow by the hydrated oxide of iron. At a later period, it was submerged and then cut and worn into an uneven surface, by deep channels and fissures, through which numerous streams found their way, oftentimes cutting entirely through the formation.

  

The Niagara limestone belongs to the upper part of the Silurian of the English geologist. It has a wide range in this country, covering a large part of Wisconsin, the upper part of Illinois, and extending east to Western New York, being prominent at Niagara Falls, from which it is named.

   In this county, it is very rich in fossils, which, owing to the softness of the rock, are generally preserved as casts, and only occasionally found in perfection.

   Certain strata appearing at the river at Lyons, and in places in the northern part of the county, are almost entirely made up of casts of the pentamerous ; in other strata, encrinites or sea-lilies are abundant. Othoceritites are found everywhere, and many specimens of trilobites and fragments of them appear, some of them being of large dimensions. Also, corals of many varieties are found, characteristic of the formation.

    It has many outcrops, especially along the streams. The bank of the Mississippi, from Lyons to the northern line of the county, is a precipitous. bluff, from one hundred to one hundred and fifty feet above the river. At the base of the cliff another and lower formation is exposed, called the Cincinnati group or formation, consisting of a bluish clay shale, and thin beds of fossiliferous limestone. This stratum is impervious to water and its junction is marked by a line of springs, some of them quite large. It has an exposure of from ten to twenty feet. As we go north, the Niagara has been entirely eroded, or washed away, and this formation caps the bluffs at Dubuque, beneath which lies the galena or lead-bearing rocks of Iowa. In places, there, it has a thickness of from sixty to eighty feet, so that only a small portion of it is exposed in this county. From Clinton, the river bears to the west, and the bluffs trend to the southwest, and are rounded and covered with soil, and raise more gradually to the prairie level. Some of the strata furnish excellent lime, and a very fair quality of building stone, but it is not very durable, being soft and porous, and disintegrates under the influence of air and moisture. It makes a very poor material for roadways, as it soon slacks and falls to pieces when exposed to moisture and wear. Streets macadamized with it show nothing but mud or dust in a year’s time.

   Over this uneven surface, in a later epoch, was again deposited, at a uniform level, the drift, or the soil and subsoil of the prairie.  When the water again receded, it cut numerous channels, sometimes coinciding with those in the bed-rock, at other times not.  These great floods have left their marks, so that the surface of the county, especially in its eastern portion, is very uneven.  The material of the drift is the same as that over the greater part of the eastern slope of the State and of Illinois.  The stratum of clay and sand, and the accumulated vegetable matter of long ages, making a soil surpassed in depth and fertility by none in the world.

    It contains bowlders and gravel of granite, quartz and other primitive rocks, with an occasional module of native copper, showing that the material came from the upper part of Dakota and the lower part of Lake Superior. In many places in the limestone there are found large caves, or pockets, filled with fire-clay, containing carbonaceous materials.  This clay is white and pure, unless colored by vegetable matter. These caves are always connected with openings at the surface of the rock, and must have been filled during the period when the water swept over them and vegetation flourished elsewhere, but prior to the “Drift Period,” as they are covered by that deposit, and hold nothing in common with it.

    The lower bluffs, along the Mississippi, are another formation, called the “modified drift,” which is made up of materials that have been dissolved from the original drift and redeposited. These deposits are left on the banks of the present river, at a height of from eighty to a hundred feet, showing that at some not very remote geological period the river flowed at a much higher level, through which it cut its present channel. In these bluffs of “modified drift” are found pieces of wood, land shells and bones of extinct land animals, demonstrating that, at some time after the prairies became dry land, the river was obstructed and its bed filled up. Geologists refer to this as the “Glacial” or ice period, when this northern hemisphere had a climate like that of Greenland.

    No mineral deposits have ever been found in this county. The Niagara limestone generally shows no indications of such. Another formation of eighty feet or more separates it from the “ Galena,” which contains the lead. Silver, iron or copper have never been found in such rock. The occasional pieces of lead ore, native copper, iron, and perhaps silver, found in the soil, have been brought from a long distance by the ice and currents, that deposited the other materials of the drift. It is evident that the bed-rock came to the surface, or was in a very shallow sea, for a long time, while the vegetable matter was deposited to form the coal in the lower part of the State; and there are occasional basins, where the carboniferous formation rests on this rock. So that it is not impossible that indications of coal may be found, but there is no probability of anything more, as, generally, the bed-rock is near the surface, and no coal ever existed below that.

    We have no space to discuss the question of the origin of treeless prairies. There is no doubt, however, but that the annual fires prevented the growth, or spread of forests. Along the alluvial bottoms of the rivers, trees flourished, and on the then clay soil of some of the bluffs, a hardy race of trees existed. The soil everywhere bears forest and fruit trees luxuriantly, when planted, and protected from fires. Most, or all of the prairie is now cultivated, but many of the old settlers can remember when annual fires swept over the uncultivated land. Oak openings, or groves of thinly-scattered trees of a hardy kind, existed in many places on the clayey knolls, which did not produce much grass.  On the moist alluvial bottoms, a thick growth of silver maples, white birch, ash and elms flourished, together with willows, water-oaks and black walnuts.  Next to the precipitous banks, especially of the Mississippi, a high, rocky soil was formed, where the hard or sugar maples are found, and a Flora common to high, stony land.

   The geology of the county furnishes an interesting study of considerable variety, as we have briefly indicated. There is no promise of mineral wealth, but a deep, rich soil abounds, capable of bringing to perfection fruit and forest trees, and all the grains and vegetables of the latitude.

   * The Historian is indebted to Prof. P. J. Farnsworth, M. D., for the chapter on Geology, and for other valuable scientific data. 

METEOROLOGY. 

    From railway surveys, it has been pretty accurately determined that low water in the Mississippi, at Clinton, is 587 feet above the sea level. It is fifty-nine feet higher than at Davenport, forty miles below. The level portions of Clinton and Lyons are from fifteen to twenty feet above low water, and from 150 to 200 feet lower than the prairie, so that the greater part of the county is from 600 to 700 feet above the level of the sea.

    From meteorological records kept at Lyons and Clinton, since 1857, the mean yearly temperature of three daily observations, is a little over 45.5 degrees Fah., varying from 45.5° to 45.75°. The lowest recorded temperature was during the last days of December and the first weeks of January, when, for three of the years observed, the mercury fell from twenty-four to thirty degrees below zero, Fah. These were exceptional years, usually 10°, and often zero is the lowest mark noted. July is the warmest month, and in several seasons the thermometer has reached 96°, or even higher. Many thermometers have recorded temperature various degrees above 100°; but, of course, they were either cheap and unreliable instruments, or so located that they were valueless for scientific purposes. Many seasons, the July heat has not ranged above 85°. The daily mean recorded from 1860 to 1872, for January, was 21°, for July, 72.6°.   Several points of coincident low temperature have been observed during a period of fifteen years. One occurs about the middle of May; another, usually producing frost, happens during the last days of August, or the first of September. In 1863, the corn was greatly injured by this latter cold snap. Since then, there has not been one so severe. Snow makes its first appearance in the week of the 20th of October. It disappears, and is followed by a long period of “Indian summer,” sometimes lasting into December. Ice forms in the Mississippi in some seasons by the 10th of November, but only in a few seasons has it been frozen across before December, when it is almost always frozen over; sometimes, however, to again open and re-close during the cold days above mentioned, of the last of December and first of January. The Mississippi generally opens by the first of March. Some seasons it has scarcely closed, and in a few the ice has remained until the first of April. The latest frost noted, was May 26, the earliest September 1, except in 1863, when frost occurred in every month of the year, except July.

    Generally the climate is warmer than in the same latitudes in the Eastern States, and also more equable. For about half the time observed, March was a fine spring month, the others were cold and blustering. December has about the same record. For some seasons, the fall of snow was very slight. In 1862, 1864 and 1870, the fall was only from seven to ten inches. In other years is has been as much as sixty inches, but it rarely remains long, so that sleighing it quite uncertain. In only two of the years noted did it last for one hundred days.  The rainfall, including melted snow, ranges from twenty-eight to forty-eight inches.  At Iowa City, 74.49 inches of water are reported to have fallen in 1851, and in 1854, but 23.35 inches.  Probably the amount of rainfall in Clinton County did not vary greatly from the above record during those years.  The heaviest rainfalls on record were in August, 1866, and July, 1879, when fully three inches of rain fell in as many hours.

    The proximity of the county to the Great Lakes modifies its climate and prevailing winds, as well as the rainfall. It has been shown that the isothermal line passes in a southwesterly direction across the county. While it is on the parallel of Chicago, the easterly winds and storms came from the direction of Milwaukee or Racine. An atmosphere charged with moisture comes with a north-of-east wind, which is precipitated by a cool northwest current. East winds bear moisture; northwest winds are dry. Violent winds and rain-storms with tornadoes, come from the southwest, changing to West and northwest. Northwest winds, after the moisture is condensed by them and precipitated as rain, are dry and oftentimes cool. The lowest temperature of winter is usually ushered in by a fierce northwest wind, blowing from one to three days, and called an Iowa “blizzard.” There are occasional periods of drought during the latter part of summer when it is noticed that the upper current of air blows constantly from the northwest. This wind is healthful and stimulating to the human system, and during its prevalence there is always a marked improvement in the public health.

    The absolute difference in temperature or average moisture between the different portions of the county are, contrary to general opinion, very slight; but in localities sheltered from the northwest wind, the apparent cold is much less and heat considerably augmented. The meteorological disturbances known as tornadoes have been the worst enemy with which dwellers in Clinton County have had to contend. Not only have they done vast pecuniary injury, and caused an amount of personal suffering, immeasurable in money, but by exaggerated reports of their terrors and frequency, both investments and immigrants have been to a certain extent frightened away from the State and county. Not only has this been the case but the tradition and recollection of the “rushing, mighty winds" of ‘44 and ‘60, fully discussed elsewhere, has always sufficed to throw the timid and nervous into a panic, and sometimes intimidate those usually brave enough, whenever a summer wind and thunder storm arises of unusually threatening appearance. The advance of scientific knowledge, though as yet unable to suggest any way of preventing or neutralizing such storms has, by increasing popular knowledge into their laws, somewhat shorn them of their pristine terrors, as positive knowledge always lessens the terrors of the vague and unknown. It is now pretty well established that any such visitation as that of 1860 is altogether exceptional, and that tornadoes, so far from being a peculiarity of Iowa, or even the plains of the Mississippi Valley, prevail at certain seasons of the year in every State in the Union, and that it is a popular error to suppose there is any tendency for them to increase in frequency or violence. A good barometer will always give sufficient warning of any severe storm.

    The cause of tornadoes is not definitely understood, but they are probably due to counter-currents of air, caused by unequal heating and rarefication, conjoined with the meeting of aerial currents flowing in the same direction, resulting in the same spiral whirl or funnel as may be observed in similar currents of water. Possibly the science of the future will show their intimate correlation with electric conditions.

SOURCE:  Allen, L. P., History of Clinton County, Iowa, Containing A History of the County, it's Cities, Towns, Etc. and Biographical Sketches of Citizens, War Record of it's Volunteers in the late Rebellion, General and Local Statistics, Portraits of Early Settlers and Prominent Men, History of the Northwest, History of Iowa, Map of Clinton County, Constitution of the United States, Miscellaneous Matters, &c, &c., Illustrated.  Chicago IL; Western Historical Company, 1879

 

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