WORRIED.--1. In all probability your sister would get better and stronger after marriage. Of course it depends a good deal upon the cause of her malady. She had far better go to her family doctor and get his advice upon the matter. We cannot take the responsibility of giving a definite answer to your question from such a very scanty amount of information.--2. There are so many books on travel and science, suitable to ordinary readers, that it is rather difficult to choose any particular volume. One of the best books on science for a beginner--that is, a person who is beginning to read science--is a little work called _Ants and their Ways_, by the Rev. Farren White. It is a charming little volume which will instil into anyone who reads it the habit of observation--so all-important in science. The book is very moderate in price. It is published by the Religious Tract Society. If you turn to the advertisement sheets at the back of this paper you will see notices of a number of very good books on both science and travel. MATRON.--Obviously the book you want is the _British Pharmacopœia_. This gives definite instructions how to make up every official preparation. There is a new edition just published. For the drugs which are not in the _British Pharmacopœia_, Squire's _Companion to the British Pharmacopœia_ may be consulted. You will do well to thoroughly master the decimal measures, and to use them exclusively, as they are now official and will alone be used in the future. The old and confusing apothecaries' measures are now out of date.