MACHINERY: When to put it in.—There is an economic law govern ing question of changing machinery. Old machinery wears out and gets out of date and has to be replaced by newer machinery that will do the work better and quicker. In some cases new machinery has to be put in on account of change of fashions or change of user. The economic law is as follows': A new machine, or group of machines, may be put in place of machines that Pre doing certain work when the increased profit brought by the new machines during their useful life is sufficient to pay the whole cost of installing them and all incidental expenses and to leave a substantial margin. Unless the estimate shows a substantial margin of probable profit from the new machine over the old ones it is not economical to replace the old machine, no matter how ancient it may be. The cost of installing the new machine, or group of machines, is made up of the following items : The cost of the machine or machines themselves, including delivery at the works, and any charges for packing ; the cost of fixing the hew machines; the cost of training men to work the new machines ; the cost of advertising the fact that the new machines are in use ; any losses incidental to the change. Among losses incidental to the change of machinery are : Loss on objects made by the old machine that may have to be scrapped or sold for a low figure ; loss of business and waste of men's time when changing from one machine to the other. From the total cost of installing the new machines may be deducted any sum realised from the sale of the old machines. The old machines may be sold to small manufacturers who can make use of them, but more probably they will have to be scrapped, and the realised value will be only that of old metal. From the value as old metal must be taken the expense of breaking up or otherwise dealing with the old machines and delivering them to the old metal dealer. The sources of profit to be obtained from the installation of new machines may be from the following : from decreased cost of producing any article, or any part of an article ; from increased selling price of the finished article. There is also the case where the market has been practically lost for a given article, owing to the machines employed turning it out in an obsolete form, and the new machine has to recover the market. Care must be taken in estimating the profits
obtainable from the use of the new machines. Estimate as carefully as possible the number of articles made by the new machines that will probably be sold during the useful life of the machine. Estimate carefully, and not too liberally, the increased profit obtainable from each of the new articles. Theproduct of these two quantities is the total profit that may be hoped for, and it is wise to rather discount the total amount owing to the uncertainty of all markets. If this amount is not greater than the amount that has been estimated to be the cost of putting in the new machines, and by a substantial figure, it is not economical to change. One of the most difficult parts of the problem is estimating the number of articles likely to he sold, and must be left to each individual manufacturer. Probably the safest plan will be to' take out sales of the article in previous years, when the old machines were good, to allow something substantial for competition, and, on the other hand, to allow something, not too substantial, for the probability of increased users. Estimating the useful life of the machine is also a very difficult matter. The useful life of the machine will depend upon a number of what mathematicians call independent variables. It depends upon possible changes in fashion, even in engineering work, and upon the progress of invention. Engineers copy each other very much, and when a fashion sets in for a particular machine, or a particular method of performing any work, engineers are very apt to follow each other, and machines are turned out almost exact copies of each other, to do the same work. Inventors also copy each other very closely. On the other hand, epoch-marking in ventions are suddenly sprung upon the market which alter the whole trend of invention, and lead to rapid developments in particular directions. The safest plan, again, will be for the manufacturer to look into the history of the machinery in question, to note the times when important improve ments have taken place, and to assume rather an early improvement than a later one.