ON DRAUGHT. 521 



the question which' relates to the slow transport of heavy goods, as being the 

 most important branch of the subject, especially for agricultural purposes. 

 Economy is, of course, the grand desideratum in the consideration of this 

 question ; consequently, the comparative expense of the two powers, supposing 

 them for the moment equally convenient and applicable, will first demand our 

 attention. 



A difficulty arises here, however, from the want of a certain measure of com- 

 parison. The power of a one-horse engine is by no means exactly the same thing 

 as that of a horse. As we have before stated, the mode of applying them being 

 different, the variations in the results are different, and consequently the effects 

 do not bear a constant proportion to each other, in different circumstances : 

 we must therefore be careful' not to fall into the mistake which we have our- 

 selves pointed out as a very common source of error, viz., the drawing general 

 conclusions from data obtained in a particular case. We shall take the power 

 of the horse, and that of the steam-engine as ascertained practically on railways, 

 where the effect of each is less influenced by accidental circumstances, and con- 

 sequently can be better ascertained than on a road. We shall confine our 

 calculations of expense to this particular case, and then endeavour to discover 

 how far the same results are to be expected, or what modifications are likely to 

 take place, and what alterations are to be made in the results under different 

 circumstances. As regards the first, viz., the comparative cost of animal and 

 mechanical power on a railway, we cannot do better than quote the words of tho 

 late Mr. Tredgold upon this subject, and we accordingly extract the following 

 passage from his work upon Railways : — 



" The relative expense of different moving powers for railways is an inter- 

 esting inquiry, and the same materials being necessary to estimate the absolute 

 expense for any time or place, it is desirable to give some particulars to aid the 

 researches of those who wish to make such comparative estimates. The annual 

 expense of a horse depends on — 



" 1. The interest of purchase-money. 



'* 2. Decrease of value. 



" 3. Hazard of loss. 



"4. Value of food. 



" 5. Harness, shoeing, and farriery. 



"6. Rent of stabling. 



" 7. Expense of attendance. 



" According to the average duration of a horse in a state fit for labour, of 

 the description required on a railway, the first three items may be estimated 

 at one-fourth of the purchase-money ; the food, harness, shoeing, &c, included 

 in the 4th, 6th, and Gth, will most likely not exceeed 40/. per annum, nor yet 

 be much short of that amount ; and supposing one man to attend to two horses, 

 this would add 15/. 12*. if the man's wages were 2*. per day ; and, at this rate, 

 the labour of a horse of the value of 20/. would cost 60/. 12*. per year; 

 or, since there are 312 working days in the year, the daily expense would 

 be 3*. lOfrf., or 186 farthings. But the power of a horse is about 1261bs. when 

 travelling at the rate of three miles per hour, and the days' work eighteen miles. 



" The annual expense of a high-pressure locomotive engine, or steam carriage, 

 consists of — 



" 1. The interest of the first cost. 



41 2. Decrease of value. 



"3. Hazard of accidents. &to 



"4. Value of coals and water. flP> 



" 5. Renewals and repairs. 



" 6. Expense of attendance. 



