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.