LATEST RECORDER 4&7 



as very careful adjustments must be made to the tension on the gauze bandings (by 

 means of brakes on the spools) and to the friction drive to the storage spool. With a 

 rolling ship and polar temperatures such adjustments could only be made with diffi- 

 culty. This is overcome in later models by making all these parts on a removable frame 

 which can be loaded in the laboratory and subsequently fitted into the machine. The 

 preservation device was not adequate, too much formalin being lost by diffusion (see 

 new model, p. 469). Stoppages frequently occurred owing to the gauze bandings 

 sticking to the driving rollers and being wound up on them ; this was overcome by a 

 comb-like device fitting into recesses in the roller (p. 469). The friction drive for the 

 storage spool was a frequent cause of trouble. It consisted of a loose spindle passing 

 through the spool, slotted so that it could be increased or reduced in diameter to hold 

 the spool more or less tightly as desired; it was a simple but inefficient device (see 

 improvement, Fig. 9). The driving rollers sometimes failed to grip the gauze sufficiently 

 (see improvement, p. 469). A number of other minor defects which need not be detailed 

 were put right during the course of the voyage. It may be noted that the power generated 

 at the driving rollers is approximately | h.p., so that pins, etc., used in securing parts 

 of rollers must be of sufficient strength. 



THE LATEST MACHINE 



It will be convenient to divide the account of the new machine into two parts, the 

 first being a general description of its working and essential features and the second a 

 full account of its detailed construction which will probably interest only those contem- 

 plating building similar machines. It will again be assumed that the reader has already 

 read the section on the general principles employed (pp. 461-464). 



The second machine (Type II) was similar in most respects to that about to be 

 described. Eight machines of this type have been made. Improvements and modifi- 

 cations have been incorporated from time to time, and the description given below 

 refers to the latest machine which may be termed Type II Modified. 



GENERAL DESCRIPTION 

 In designing the new machine the defects already noted in the original model were 

 kept in mind. It was desirable to make the machine as small and compact as was 

 compatible with stability in the water and efficiency in plankton sampling. In the 

 original machine the gauze bandings were 8 in. wide, 6 in. of which were exposed in the 

 water tunnel; in the new machine the width of the gauze was reduced to 6 in., a width 

 of 4 in. being exposed. Since the cross-section of the tunnel has to be rectangular, to 

 match the rectangular sections on the gauze banding, considerable space was wasted in 

 the first machine by making the outside body cylindrical. I decided to make the new 

 machine rectangular in form. The latest machine is illustrated in Plate III and in 

 Figs. 3-16. The rectangular cross-section in no way interferes with the stability of the 

 machine; indeed it is likely that its vertical sides help to prevent lateral movement as 

 do the side panels of a box kite. The main body was thus made as a box frame 6| in. 



