The availability of accurate representations of the Earth's magnetic field for the past 25 years allows us to study the typical rates of change of the field as a function of the degree of the spherical harmonic. It is shown that there is a general increase in the relative rate of change as the degree of harmonic is increased. The analysis was only carried out to degree eight harmonics, because knowledge of the rate of change of the higher degrees is poor. If the projected rate of change continues in the same manner for higher degrees, then it is predicted that harmonics of, say, degree 14 will change at a rate of about 6% per year. This will mean that it should be easy to determine whether harmonics higher than degree fourteen originate in the core or whether they are caused by crustal magnetization. Although westward drift of the field does not necessarily tell us about motions of the core fluid at the core mantle boundary, it is probably true that these motions depend on the same parameters as those used to determine the westward drift. Since the westward drift depends on the longitudinal gradient of the component of field under consideration, it generally depends more on the higher orders of harmonic within each degree than on the lower orders, all other things being equal. In fact, not all other things are equal, because it is shown that in general the power in the higher orders of harmonic is less than the power in the lower orders. Another important factor in determining longitudinal motions is that it is the field at the core mantle boundary which is important, not the field at the Earth's surface. This results in the higher degrees being relatively more important than at the surface of the Earth. But because of the longitudinal differentiation, it turns out that in order to determine a major portion of the longitudinal drift it is necessary to have information about harmonics up to about degree 20. Therefore, with knowledge only of degrees eight or less, we really know rather little about longitudinal motions. Evidence for secular acceleration was found. Not surprisingly, the average rate of secular acceleration