Each and every tax must be studied in its proper connection if it is desired to know to what extent the aims of taxation arerealised. Sometimes the shifting of the tax defeatsthe general purpose, as inthe case of the tax on the mortgagee's interest in California, while in others the general purpose can only be accomplished when the tax is shifted. The process of shifting, like every other economic transfer of burdens, costs something. No person advances the amount of the tax with the intention of transferring it to some other without desiring to be paid for his trouble and risk. Unless the conditions are against him he will succeed in getting paid for it. Thus, the importer of books tries to get a certain profit on the cost to him, which is composed of the price in England plus the cost of transportation and the duty. If the rate of profit or commission which he reckons is 10 per cent, he adds 10 per cent of the duty as well as of the other items. The money which he has advanced on the duty must bring him its share of the earnings. So in the case of the mortgages in California. One-quarter of one per cent interest, or more, is usually charged above the rate plus the tax. If the lender has to suffer the annoyance and run the risk of paying the tax, he will have to be reimbursed. Shifting is, therefore, an undesirable and costly process, and is to be avoided unless there is some clear saving, as in the case of the customs duties.