for the same lots at room temperature ranged from 0.76 to 2.11 grams with a 60-micron needle. Similar differences in the pressure required to puncture the warm and cold fruits were obtained when the fruit was allowed to remain in the ice box 24 hours. Washing the berries in tap water did not appreciably affect their resistance to puncture one way or the other. This may be due to the fact that the berries were tested immediately on removal from the water, which would preclude any appreciable cooling effect from evaporation. The results with Montmorency cherries were practically the same as those with berries. Cooling the fruit increased its resistance to puncture. From these results it is evident that the fruits used in the work are much less easily punctured when cool than when warm. It seems probable that this increase in the resistance of the skin to mechanical injury is an important factor in the results obtained by Ramsey, Stevens and Wilcox, and Ridley in their work on the prompt cooling and refrigeration of berries. It would seem also that the picking of berries in the early morning when they are cool, as is quite commonly practiced in some regions, would be decidedly advantageous, in spite of the fact that at that time the berries are frequently wet with dew, as no evidence was obtained that moist berries were more susceptible to injury than dry fruits. No attempt was made to determine the reason for this increase in resistance to puncture due to cooling. A possible explanation of this phenomenon, which occurred to the writers, was that the surface of the fruit might be covered with a wax which softened at the higher temperatures but became harder and more resistant when cooled. Another purely mechanical explanation is that the walls of the drupelets or of the external cells of the fruits have a lower coefficient of expansion than their contents. If this were the case, at higher temperatures the walls would be under greater strain and would, therefore, puncture more easily. This point deserves further investigation. In conclusion, it has been shown in this work with strawberries, blackberries, black and red raspberries, and cherries that cooling the fruit renders the epidermis more resistant to mechanical injury. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM 5 CENTS PER COPY A NOTATION. Unless otherwise noted, the various symbols used throughout this publication will have the following significance: H-Effective head, in feet. H-Loss of head at entrance of siphon, in feet. in feet. H-Loss of head due to contractions in siphon, in feet. V-Velocity, at throat of siphon unless otherwise noted, in feet per second. A-Area of cross section treated, in square feet. k-A coefficient in the formula for siphon discharge, ranging from 0.50 to 0.80 and usually assumed ac cording to the materials of construction and the form of the siphon. g-Acceleration of velocity due to gravity, 32.16 feet per second per second. C-A coefficient, in the formula for weir discharge varying from 2.5 to 4.5 and determined from experi ments on small model weir dams under low heads. p-Height of weir in feet above the bed just upstream from weir and applied only in the Bazin formula. h-Head, in feet corresponding to velocity of approach. L-Length of weir crest, in feet. Q-Quantity of discharge, in cubic feet per second. In its ordinary use the spillway is a device for removing surplus water from a reservoir or canal, in order that the water level within the reservoir or canal may not rise above the point considered safe or fixed upon as the maximum allowable height. It is distinguished from other types of wasteways by the fact that the surplus water passes over a crest or "spills" instead of passing through openings in the dam or canal bank. The conditions necessitating spillways are many and they vary as to the requirement for capacity, the degree of safety factor demanded, by the extent or importance of the structure they protect, the location of the spillway with relation to that of the dam or canal embankment, and the functions they must perform in maintaining a more or less perfect control of the reservoir or canal in times of maximum inflow when a predetermined flowage line or freeboard must not be exceeded. This necessitates the provision for passing the highest floods over the spillway within the safe limit of maximum rise, and the conveyance of this water away without injury to the dam or canal embankments or to their appurtenant structures. If a reservoir is to be located in a stream channel where the extent of inflow is not under human control, the spillway must provide for the passage of both normal and flood flow when the reservoir is full 149907°-20-1 and must protect the dam or embankment from being topped.if it has not sufficient structural resistance to withstand the resultant shock, pressure, and vibration imposed upon it by overflow of considerable depth. In the case of earth dams or embankments it is necessary to provide a means for conveying the falling water away from the point where the embankment strikes the surface below it. An elaborate method resorted to in accomplishing this purpose is shown in figures 1 and 2, Plate I, illustrating a system of drops and a' stilling pool at the foot of the Lahontan Dam in Nevada. In any case it is necessary to provide a means of neutralizing the energy developed in the fall of the water over the dam at the point where it strikes the stream below so as not to endanger the structure by undermining it. When the reservoir is not in the stream channel the conditions under which the spillway is to operate are greatly simplified in that the flow of the water is generally regulated either by diversion of all or part of the stream flow into a channel and thence to the place of application or storage (see fig. 1, Pl. II); or it may be supplied by long conduits always controlled by some system of headworks. Under such conditions, when it is necessary to provide spillways, they are designed to pass such excess of water as may reach the reservoir by the failure of the inlet works to function properly, the accumulation of surface water due to superdrainage, or a combination of the two. Examples of spillways where there is regulated flow into the reservoir are numerous, and figures 1 and 2, Plate III, show a provision for an earthen dam in Mockingbird Canyon near Riverside, Calif., and the East Park Reservoir Dam of the Orland Project, near Orland, Calif., where there is a separate spillway and, in addition, a diversion dam and inflow control. The Roosevelt Dam shown in figure 2, Plate II, is an example of the type where the spillway is provided either in a center section or at the end, and provision made for the impact of the falling water where it strikes the stream below. The Holter Dam of the Montana Power Co., near Helena, Mont., a cross-section of which is shown in figure 4, is an example of an "ogee" type of dam provided with baffles and a water cushion to dissipate the energy developed in the overpour. With relation to spillways in connection with canals, the same general characteristics prevail and their discussion may be taken up along the same lines though more properly following the cases where the inflow is regulated. In discussion of canals, spillways and escapes are generally included in the same class of structures, called wasteways, and although they are both used as protective agencies in the canal system, they differ somewhat in their functions. They properly should be divided into two classes in that an overflow spillway is |