A man has £1,000 in gold. He has to travel or to go abroad on a war, or is not certain of the safety of so large a sum if it is kept in his house. He therefore gives it into the custody of a man whom he can trust, and who, on account of special circumstances, can keep it more securely than he himself can. What the owner of the £1,000 wants in the transaction is to be certain of getting a part or the whole of his money whenever he may need it. He does not want the individual pieces of money. So long as he can get the value of them _or of part of them_ at any moment from the man to whom he gave custody of the original sum he is satisfied. A good many other people feel the same necessity. The man who has special opportunities for looking after _all_ their sums of money collects them together and has them in his strong box in safe keeping. Those who have acted thus would be very angry if they found their money had been lost, or that when they came to ask for £20 or £100 out of their thousand pounds--needing such a sum for the transactions of the moment--the man in whose custody the whole lay was unable to let them have the £20 or £100 required. But so long as the _depositor_ (as he is called, that is, the man who hands over his money for safe custody) finds himself, in practice, always getting the whole or any part of his deposit on demand, he is content; _and will not be annoyed to find that the person in whose custody he left the money has been using it in the meantime_. For instance: I might leave £1,000 in gold in the custody of someone who is better able than I to prevent its being stolen. I am saved all the trouble of looking after it, and I can call on a part of it or all of it whenever I like. If there were only myself leaving it thus with one friend, and it was a particular transaction between us two, that friend would be acting wrongly if he were to take my £1,000 and buy a ship with it, say, and do trade. No doubt he would earn a profit, and could say to me when I came back for £100 of it: “I am sorry that I cannot give you your £100, but I have used the money, without telling you, to buy a ship. The ship will earn a profit of £200 at the end of the year, and then you can have back your £100 if you like, and if you press me, I will even sell the ship and you shall have back the whole of your £1,000.” In that case I should naturally answer: “No one gave you leave to use my money. You have embezzled it, and you have acted like a thief.”