which these processes take place, and to find the common equation for all of them.

1. On the Velocity of Solidification of Over-cooled Liquids, of Solutions, and of Liquid Mixtures. From the experiments of Moore, made in Ostwald's laboratory,' the author shows that the equation =c(tt) is to be applied for the velocity

dx
dz

of solidification, where t is the actually existing temperature of the over-cooled liquid, to the temperature, where the solid and liquid solution are in equilibrium, since beginning with the greater differences (instead of as has been done by Moore, with the smaller) t-t, it is easy to show that to (dx : dz)t,

dr

dz

=

tot (dx: az)t,,

2. On the Velocity of Crystallisation of Over-cooled Liquids and Solutions.The same equation = c(t −t) is found to be applied for the velocity of crystallisation. Now, since the separation of the solid solvent is accompanied by evolution of heat (latent heat of melting), and the increase of the temperature of the liquid is directly proportional to the quantity of separated ice, we can, instead of dt the above equation, put = c'(to-t), where c' is directly proportional to the latent dz heat of melting, and inversely proportional to the specific heat of the liquid. Very careful measurements have been carried out. The liquid was at first over-cooled to below its freezing-point; the distance from the freezing-point was then measured on the 01° thermometer, and the time noted by my assistant to second.

3. On the Velocity of Melting of Solid Solvents in the Warmer Liquids and dt Solutions. For the process of melting, Newton's equation = c(t − t) for conducdz tion is to be used; the convergence temperature is here that at which ice and liquid are in equilibrium, i.e., the freezing-point; the ice plays here the part of the cooling medium, abstracting heat from the liquid. Since now the velocity of reaction takes place through the ice-surface, the velocity of reaction at a given time z will be also directly proportional to the surface of the ice present in the liquid at the dt time . Our equation can therefore get the form=c'(t-t)0, where O is in dz proportion to the surface of the ice. The liquid or solution to be investigated is at first over-cooled 1° or 1°2 below its freezing-temperature; the ice is then crystallised. After the separation of the ice we allow the ice to rise in the beaker to the upper part of the liquid, warm the liquid to about 0°3 or 0°-4 above the freezing-point; the liquid is then stirred, the temperature rises at first, and after reaching its maximum falls. The time is measured to second.

We have therefore investigated two classes of reactions before perfect equilibrium takes place. The first is where the temperature of both parts of the heterogeneous system is below or above the temperature of equilibrium (solidification, dx crystallisation). For this class we have to apply the equation = c(t-t) or dz

dt

dz

= c′(t。 − t), which in its form, but not in its purport, is identical with Newton's equation for conduction. The second class is where one of the parts of the heterogeneous system is at the temperature of equilibrium and the other is above or below that of equilibrium (melting process in liquids). The velocity of these processes is regulated by Newton's law for conduction.

As we know, we have two kinds of equilibrium, perfect and imperfect equilibrium. While in the case of perfect equilibrium (for example, ice and water) at a constant pressure, the smallest change of temperature is sufficient to cause one of the parts of the heterogeneous system to disappear, in the case of imperfect equilibrium (for example, acid + alcohol, ether + water) a small change of temperature produces only a small change in the state of equilibrium, while the relation

1 Zeitschr. phys. Chem., vol. xii. p. 545.

of the quantities of the acting parts changes in one or the other direction. The velocity of reaction, before imperfect equilibrium takes place, formed the subject of investigation of many scientists; Vernon-Harcourt and Esson, van 't Hoff, Guldberg, and Waage, should be specially mentioned. The author finds in the case of dt dz

d.x

solidification and crystallisation that the equation = c(t − t), or =c' (to-t) is

dz

dx dc

to be applied, but would express the common equation as =f(t-t), since the

velocity of the reaction can often be complicated by other phenomena.

Let us now bring into connection the equations for the two kinds of velocity of reactions with the two kinds of equilibrium.

In the case of imperfect equilibrium we have, before the state of equilibrium is arrived at, two reactions:

In the case of

and equilibrium is arrived at when c(A-x') (B—.x') = c'.x22, i.e., both reactions take place simultaneously and the equilibrium is a dynamic one. perfect equilibrium we have before the equilibrium is arrived at

dx

and equilibrium is arrived at when to-t-0 (ie., at the freezing temperature); therefore at the point of equilibrium equals 0, that is to say, no further reaction takes place, and the equilibrium is a static one.

dz

9. Chemical History of Barley Plants. By C. F. CROSS and C. SMITH. Work has been carried out over a period of two years (1894 and 1895) upon crops grown on the experimental plots at Woburn. Maximum plot 6 and minimum plot 1 were investigated with regard to the furfural and permanent tissue which they contain.

A table of results is appended to the paper.

From the table we draw the following conclusions:

1. The conditions of soil nutrition have very little influence upon the composition of the plant.

2. The feeding value of straws grown in wet seasons is high, and conversely the paper-making value of such straws is low.

3. The furfuroids are continuously assimilated to permanent tissue in a normal season, but in a dry season, on the other hand, the permanent tissue is put under contribution for nutrient material, which is ordinarily drawn from the cell contents.

SECTION C.-GEOLOGY.

PRESIDENT OF THE SECTION.-W. WHITAKER, B.A., F.R.S., F.G.S.

UNDERGROUND IN SUFFOLK AND ITS BOR pers.

WHEN the British Association revisits a town it is not unusual for the Sectional Presidents to refer to the addresses of their local predecessors, and to allude to the advance of their science since the former meeting. I have at all events tried to follow this course, with the sad result of having to chronicle a falling back rather than an advance in our methods of procedure; for at the meeting of 1851 all the Sectional Presidents had the wisdom not to give an address, and of all the inventions of later years I look upon the presidential address as perhaps the worst.

Had I the courage of my opinion I should not now trouble you; but an official life of over thirty-eight years has led me to do what I am told to do, and to suppress my own ideas of what is right. After all it is the fault of the Sections themselves that they should suffer the evil of addresses. They could disestablish the institution without difficulty.

On these occasions it is not usual to allude to the personal losses our science has had in the past year; but there are times when the lack of a familiar presence can hardly be passed over, and since we last met we have lost one of our most constant friends, who had served us long and well, and had been our Secretary for a far longer time than any other holder of that office. When we were at Cxford last summer none of us could have thought that it was our last meeting with William Topley.

I do not now mean to say anything on the origin or on the classification of the various divisions of the Crag and of the Drift that occur so plentifully around us, and form the staple interest of East Anglian geology. These subjects, which are the more interesting from being controversial, I leave to my brother-hammerers, and without claiming the credit of magnanimity in so doing, having said what I had to say on them in sundry Geological Survey Memoirs. The object of this address is to carry you below the surface, and to point out how much our knowledge of the geology of the county in which we meet has been advanced by workers in another field, by engineers and others in their search for water. As far as possible allusion will be made only to work in Suffolk; but we must occasionally invade the neighbouring counties.

This kind of evidence has chiefly accumulated since the meeting of the Association at Ipswich in 1851; for of the 476 Suffolk wells of which an account, with

1

some geologic information, has been published, only 68 were noticed before that year, all but two of these being in a single paper. The notes on all these wells are now to be found in twelve Geological Survey Memoirs that refer to the county. Number alone, however, is not the only point, and many of the later records are marked by a precision and a detail rarely approached in the older ones. It should be stated that in the above and in the following numbers strict accuracy is not professed, nor is it material. A slight error in the number of the wells, one way or the other, would make practically no difference to the general conclusions.

Now let us see how these records affect our knowledge of the various geologic formations, beginning with the newest and working downward.

The Drift.

Under this head, as a matter of convenience for the present purpose, we will include everything above the Chillesford Clay. There is no need for refinement of classification, and the thin beds that come in between that clay and the Drift in some parts do not affect the evidence we have to deal with.

As a matter of fact it is only from wells that we can tell the thickness of the Drift over most of the great plateau that this formation chiefly forms; open sections through a great thickness of Drift, to its base, are rare, except on the coast.

There is often some doubt in classifying the beds, the division between Drift and Crag being sometimes hard to make in sections of wells and borings; but from an examination of the records of these Suffolk sections that pass through any part of the Drift Series (as defined above) we find that no less than 173 show a thickness of 50 feet and upward, whilst of these 34 prove no less than 100 feet of Drift, many reaching to much more. Of the two that are said to show a thickness of over 200 feet and the one other said to be more than 300 feet deep in Drift, we can hardly feel certain; but such amounts have been recorded with certainty as occurring in the neighbouring county of Essex.

These great thicknesses (chiefly consisting of Boulder Clay) show the importance of the Drift, and the impossibility of mapping the formations beneath with any approach to accuracy, on the supposition that the Drift is stripped off, as is the case in the ordinary geologic map. The records also show the varying thickness of the Drift, and how difficult it often is therefore to estimate the thickness at a given spot. Sometimes the sections seem to point to the existence of channels filled with Drift, such as are found also in Essex and in Norfolk; and it may be noted that in the northern inland part of the former county, one of these channels has been traced, though of course not continuously, for some 11 miles along the valley of the Cam, and at one place to the depth of 340 feet (or nearly 140 below sea-level), the bottom of the Drift moreover not having been reached even then. A channel of this sort seems to occur close to us, in the midst of the town of Ipswich, where, by St. Peter's, one boring has pierced 70 feet of Drift, and another 127, in ground but little above the sea-level.

As the Drift sands and gravels, that in many places occur below the Boulder Clay, often yield a fair amount of water, the proof of their occurrence and of the thickness of the overlying clay is of some practical good.

The Crag.

On this geologic division we have a less amount of information, as would be expected from the fact that it is not nearly so widespread as the Drift, and this information is confined to the Upper, or Red, Crag, the Lower, or Coralline, Crag occurring only over a very small area, and no evidence of its underground extension being given by wells.

What we learn of the Red Crag, however, is of interest, several wells having proved that it is far thicker underground than would have been supposed from what is seen where its base crops out. One characteristic, indeed, of this sandy deposit, in the many parts where it can be seen from top to bottom, is its thinness,

as in such places it rarely reaches a thickness of 40 feet. But, on the other hand, wells at Hoxne seem to prove more than 60 feet of Crag, whilst at Saxmundham the formation is 100 feet thick, and at Leiston and Southwold over 140. Further north, just within the border of Suffolk, there is, at Beccles, a thickness of 80 feet of sand, or, with the overlying Chillesford Clay, a total of 95. Our underground information has, then, trebled the known thickness of the Upper Crag of Suffolk.

It has also shown that at some depth underground the colour-name is a misnomer, the shelly sands being light-coloured and not red. This is the case too with some other deposits, which owe their reddish-brown colour at the surface to peroxide of iron. Presumably the iron-salt is in a lower state of oxidation until it comes within reach of surface-actions. This seems to point to the risk of taking colour as the mark of a geologic formation.

Eocene Tertiaries.

Below the Crag there is a great gap in the geologic series, and we come to some of the lower of the Tertiary formations, about which little had been published, as regards Suffolk, before the work of the Geological Survey in the county. It seems as if the special interest in the more local Crag had led observers to neglect these beds, which had been amply noticed in other parts.

We have records of more than forty wells in Suffolk that are partly in these deposits, and of these thirty-six reach down to the Chalk, twenty giving good sections from the London Clay to the Chalk. The thickness of the Lower London Tertiaries (between those formations) thus proved varies from 30 to 793 feet, the higher figure being much greater than anything shown at the outcrop. The greatest recorded thickness is at Leiston, where, moreover, the top 26 feet of the 79 may belong to the uppermost and most local of the three divisions of the Series, the Oldhaven Beds, of very rare occurrence in the county. The next greatest thickness is at Southwold, where the whole has been classed as Reading Beds (the persistent division), though here and elsewhere it is possible that the underlying Thanet Beds are thinly represented. It is noteworthy that at both these places, where the Lower London Tertiaries are thick, they are also at a great depth, beginning at 252 and 218 feet respectively, which looks as if, like the Crag, they thickened in their underground course away from the outcrop.

The important evidence given by these wells, however, is not as regards thickness; it is to show the underground extent of the older Tertiary beds, beneath the great sheet of Crag and Drift that prevents them from coming to the surface north-eastward from the neighbourhood of Woodbridge. It is clear that over this large tract we can know nothing of the beds beneath the Crag otherwise than from wells and borings; and, until these were made, our older geologic maps cut off the older Tertiary beds far south of the parts to which we now know that they reach, though hidden from our sight. No one, for instance, would have imagined many years ago that at Southwold the Chalk would not be touched till a boring had reached the depth of 323 feet, or some 280 below sea-level, or that at Leiston those figures would be about 297 and 240.

It is from calculations based on the levels of the junction of the Chalk and the Tertiary beds in many wells that the line engraved on the Geological Survey map as the probable boundary of the latter beds under the Crag and Drift has been drawn. From what has gone before, however, as to the great irregularity in the thickness of the Drift, it is clear that this line must be taken only as approximate, and open to correction as further evidence is got; albeit the junction of the Chalk and the Tertiary beds is found to be here, as elsewhere, fairly even, along an inclined plane that sinks toward the coast.

Cretaceous Beds.

Though the Chalk is reached by very many wells, yet we get less information about it, by reason of its great thickness. Moreover, the great amount of overlying beds in many cases is a bar to deep exploration.