Reflecting upon the natural method of computing present time, it shows how far from truth we may be led by the irregular power of passion. Nor are our eyes immediately opened when the scene is past: the deception continues while there remain any traces of the passion. But looking back upon past time when the joy or distress is no longer remembered, the computation we make is very different. In this situation, passion being out of the question, we apply the ordinary measure, viz. the course of our perceptions; and I shall now proceed to the errors that this measure is subjected to. In order to have an accurate notion of this matter, we must distinguish betwixt a train of perceptions, and a train of ideas. Real objects make a strong impression, and are faithfully remembered. Ideas, on the contrary, however entertaining at the time, are apt to escape an after recollection. Hence it is, that in retrospection, the time that was employed upon real objects, appears longer than the time that was employed upon ideas. The former are more accurately recollected than the latter; and we measure the time by the number that is recollected. I proceed to particulars. After finishing a journey through a populous country, the frequency of agreeable objects distinctly recollected by the traveller, makes the time spent in the journey appear to him longer than it was in reality. This is chiefly remarkable in a first journey, where every object is new and makes a strong impression. On the other hand, after finishing a journey through a barren country thinly peopled, the time appears short, being measured by the number of objects, which were few and far from interesting. Here in both instances a reckoning is brought out, directly opposite to that made during the journey. And this, by the way, serves to account for a thing which may appear singular, that in a barren country the computed miles are always longer, than near the capital, where the country is rich and populous. The traveller has no natural measure of the space gone through, other than the time bestowed upon it; nor any natural measure of the time, other than the number of his perceptions. These being proportioned to the number of visible objects, he imagines that he hath consumed more time on his day’s journey, and accomplished a greater number of miles, in a populous than in a waste country. By this method of calculation, every computed mile in the former must in reality be shorter than in the latter.
Again, the travelling with an agreeable companion produceth a short computation both of the road and of time; especially if there be few objects that demand attention, or if the objects be familiar. The case is the same of young people at a ball, or of a joyous company over a bottle. The ideas with which they have been entertained, being transitory, escape the memory. After all is over, they reflect that they have been much diverted, but scarce can say about what.
When one is totally occupied in any agreeable work that admits not many objects, time runs on without observation; and upon an after recollection must appear short, in proportion to the paucity of objects. This is still more remarkable in close contemplation and in deep thinking, where the train, composed wholly of ideas, proceeds with an extreme slow pace. Not only are the ideas few in number, but are apt to escape an after-reckoning. The like false reckoning of time may proceed from an opposite state of mind. In a reverie, where ideas float at random without making any impression, time goes on unheeded and the reckoning is lost. A reverie may be so profound as to prevent the recollection of any one idea: that the mind was busied in a train of thinking, will in general be remembered; but what was the subject, has quite escaped the memory. In such a case, we are altogether at a loss about the time: we have no data for making a computation. No cause produceth so false a reckoning of time, as immoderate grief. The mind, in this state, is violently attached to a single object, and admits not a different thought. Any other object breaking in, is instantly banished, so as scarce to give an appearance of succession. In a reverie, we are uncertain of the time that is past: but in the example now given, there is an appearance of certainty, so far as the natural measure of time can be trusted, that the time must have been short, when the perceptions are so few in number.
The natural measure of space appears more obscure than that of time. I venture however to enter upon it, leaving it to be further prosecuted, if it be thought of any importance.
The space marked out for a house, appears considerably larger after it is divided into its proper parts. A piece of ground appears larger after it is surrounded with a fence; and still larger when it is made a garden and divided into different copartments.
On the contrary, a large plain looks less after it is divided into parts. The sea must be excepted, which looks less from that very circumstance of not being divided into parts.
A room of a moderate size appears larger when properly furnished. But when a very large room is furnished, I doubt whether it be not lessened in appearance.
A room of a moderate size, looks less by having a ceiling lower than in proportion. The same low ceiling makes a very large room look larger than it is in reality.
These experiments are by far too small a stock for a general theory. But they are all that occur at present; and without attempting any regular system, I shall satisfy myself with a few conjectures.
The largest angle of vision seems to me the natural measure of space. The eye is the only judge; and in examining with it the size of any plain, or the length of any line, the most accurate method that can be taken is, to run over the object in parts. The largest part that can be taken in at one stedfast look, determines the largest angle of vision; and when that angle is given, one may institute a calculation by trying with the eye how many of these parts are in the whole.