READING LESSONS.

THIRD BOOK.

Mental Culture.

BY EDWARD PURCELL.

LESSON I.

OBSERVATION AND EXPERIMENT.

"Days should speak, and multitude of years should teach wisdom."

1. THERE is no feature in the aspect of nature more striking than the infinite diversity exhibited in the objects and operations surrounding us. Man, with limited powers of invention, repeats in his productions the same forms and means of accomplishing his ends, while the infinite power of the Creator is manifested in the exuberant variety of His works. Each region of the earth produces its peculiar forms of life; each tree and shrub possesses its own properties and appearance; each stone and leaf has impressed upon it some distinguishing mark. When we reflect upon the daily occurrences of life, we find a similar diversity :-each day that passes is unlike any that has preceded it; each historical event has its own special character; each century presents some new features of human existence. If we descend to the most minute forms of nature we still find this absence of sameness: no two blades of grass are precisely similar, each grain of sand submitted to the microscope shows its own peculiarities in form and colour, and it is only by a theoretical assumption that we can represent the ultimate molecules of bodies as uniform in structure.

2. Now this infinite multiplicity of objects and events is so puzzling to the mind, that knowledge would be impossible, unless we had some mode of grouping and

classifying the subjects of our thoughts. We could not retain them in the memory, or refer to them with sufficient distinctness, or convey our meaning to others. Each individual thing and event would require a separate name, so that our language would resemble the Chinese, in which, there being a distinct word for each distinct object, a lifetime is consumed in learning to' read and write. It was the perception of this difficulty which led some of the old philosophers to assert that no science could be constructed from particulars-that is, from separate facts, however numerous; and this assertion, properly understood, is not devoid of truth. We must bind our facts in bundles before they will serve for scientific purposes, and support our footsteps in the advance of knowledge; still the facts are the essential things which must be collected separately before these bundles can be formed.

3. We thus see that while classification is the first step in the formation of a science, the collection of facts must of necessity precede their arrangement. Hence the importance of our two modes of truth-collectingobservation and experiment. These are employed in obtaining a true knowledge of things previous to arrangement, and inserting new discoveries, when possible, under their respective classes. They aid us in this important work, chiefly by tracing the resemblances and differences of objects. As we have seen what great diversity exists in nature, it is manifest that no reason could be assigned for grouping together several things in one class, unless we could trace resemblances amongst a number of individuals; while, on the other hand, were not the differences accurately ascertained, the confusion of totally unlike things would be unavoidable. Our knowledge is, indeed, in a great degree comparative; we know how objects resemble, and how they differ from, each other, much better than what anything is in itself.

4. In observation we apply our faculties in examining a thing as it is, without endeavouring to alter the conditions under which it is presented to us. With a large class of objects, this is all that is possible for us to accomplish in astronomy, for instance, we cannot apply

any new force or influence to the stars and planets; we must be satisfied with examining them as they are. Yet this mere passive attention bestowed on things and events has been one of the most effective means of extending human knowledge, and enlarging our acquaintance with the characters and productions of the world we inhabit. It requires, it is true, many moral and physical qualities in the individual who pursues it-honesty, perseverance, endurance-but, supported by these, it has rendered vast benefits to the human race.

5. It has secured to us new materials for industry from remote parts of the earth and new openings for commerce; it has made our own all that other nations in the process of ages have either by chance or ingenuity invented. In past times the care of observant travellers enriched Europe by the introduction of Indian cotton, China silk, Arabian coffee, with the innumerable vegetable and animal materials, and manufacturing processes, which now form the great sources of our national wealth. Within the present century, we have seen, in the discovery of gold in Australia, the vast results that may be obtained by individual observation. An inhabitant of this great colony, who had gone to the gold regions of California, was so struck with the resemblance of the district in which the precious metal was found to one in his own country, that he returned to find, in South Australia, gold-fields more productive than those, whose world-extended renown had induced him to seek them across the ocean. Nor is this field of inquiry exhausted; there are doubtless, in foreign countries, many products which would afford useful materials for our manufacturing skill, and valuable additions to the stores of human food. The mineral, vegetable, and animal resources of the earth and ocean cannot be as yet considered completely explored; there must still remain many unknown benefits which a careful and intelligent observer may confer upon mankind.

6. New applications and improvements of the productions of our own land are likely to spring from the same A practical mineral surveyor, Mr. Smith, of

source.

Oxfordshire, may be said to have laid the foundation of geology, by pointing out that fossils indicate the identity of strata. Another gentleman of the same name effected a vast improvement in our agriculture by introducing the system of drainage of fields; indeed, it would be impossible to mention any art or manufacture into which observation has not introduced important improvements, and is not likely to introduce others, perhaps of equal value. A man who takes attentive note of all that occurs of interest in his art or profession, acquires the valuable quality of mind called practical experience. An experienced sailor knows the signs of the weather, the sets of currents, and other matters of importance to the safety of the ship, &c.

7. RECORDING OBSERVATIONS.-In the article, "How to Observe," in the first volume of this series, enough has been said for the student's guidance in the exercise of this important habit; but there is one branch of the subject of great importance not there alluded to, and which requires a few remarks in this place. I refer to the manner of representing our observations and recording them, so as to render them of future service. This may, in the majority of cases, be done by averages, per centages, or graphical delineation.

8. AVERAGES.-When a set of observations of the same kind has been made, it is generally useful to obtain an average of the whole. This is done by dividing the sum of the results by the number obtained. Thus, if the height of the thermometer be observed every hour in the course of a day, the sum of all the degrees of heat, divided by 24, will represent the average or mean temperature of that day. Similarly the sum of all these daily averages, divided by 365, will give the mean temperature of the year. In this manner averages are determined for a great variety of useful purposes, such as corn averages, &c. The average, or, as it is termed from its use in comparing different countries, the relative population of a state, is obtained by dividing the total population by the number of square miles. This process gives for Europe 70 inhabitants to the square mile, and for Australia less than 1.

The system of Life Insurance, so widely and advantageously established in this country, is based upon this principle. Thus if a record be kept of the number of years that each of one hundred men, in ordinary health and strength at thirty years of age, lives after that period, and these years be added together, the sum divided by 100 gives, as the average continuance of human life after thirty, a term of 34 years. An insurance company must therefore charge, for insuring a sum upon a life of 30 years, a series of annual payments sufficient, with the interest upon their investment, to produce at the end of thirty-four years, the sum insured for and a fair profit in addition. The experience of the large London companies during many years shows that calculations based upon this average survivorship lead to almost precisely the results anticipated. A sum of from 21. to 21. 10s. is found to be the annual payment required for each 1007. insured for on a life of 30 years.

9. PER CENTAGES.-Another convenient mode of representing our observations is that of per centages: thus, in the returns of deaths from disease, or in battle, and in the statistics of education and distribution of industrial occupations amongst a population, we find the facts often arranged as so many per cent. out of the whole. This is, of course, only a relative mode of representing a fact. If, for instance, we read that the deaths in London were in a particular week 3 per cent. of the population, we do not from this know the actual number of persons who died within the time, although, knowing what the population is, this, if required, can be easily found. The way to estimate the per centage, is to multiply the number of cases by 100, and divide the result by the number out of which they were taken. Thus, if, out of a regiment of 1125 men, there be an actual loss of 75, the casualties are 6·6 per cent. This method of representing results supplies the best possible means of comparing the condition of society at different periods, or in different countries. Applying it to education, we find that in England and Wales, in 1851, the number per cent. of children between the ages of seven and fourteen years of age at school was 50, and