Of the total cost, the fixed equipment was 60% and the motive apparatus was 40% of the cost of the whole equipment.

The combined equipment has a relative life compared with that of its most durable part, which has been assumed to be such material as elevator guides and fixed ironwork, of 40%.

The effect of the motive apparatus is, therefore, the greatest in reducing the total life of the building. The cost of the entire equipment in this case approximated 20% of the total cost, and if the building, upon dissection of its elements, should show, without equipment, a mean relative life of 77%, then the introduction of the equipment reduces the combination to 70%, or, in other words, the building alone would have a mean life of 57 3/4 years; but this would be reduced by the effect of the equipment to 52 1/2 years, involving on each one million dollars of total invested value an annual addition to the necessary sinking-fund for depreciation of about $7500 a year.

Fig. 13

In a dry-goods building the investment in the equipment and in a power plant was:

For the fixed equipment, elevators, sprinklers, and boilers for heating .... 20% of the cost of the building For the motive apparatus, or generating plant...... 6% of the cost of the building

The introduction of delicate and short-lived machinery into buildings, therefore, affects not only the proportion of funds for its own replacement, but that covering the duration of life of the entire structure.