490 G. H. DREW 



All the thermometers were made of the glass known as Jenaer 16 III, 

 and the apparent dilatation of mercury in this glass is eaVo- The 

 correction to be applied to the reading of the reverser is given by the 



formula ^ aJna ' where T = the temperature registered by the 



reverser, t = the temperature shown by the auxiliary thermometer at 

 the moment of reading, and V° = the volume, expressed in degrees of 

 the stem, of the secondary bulb and the portion of the stem below the 

 0° mark of the reverser. 



The thermometers were mounted in pairs in simple metal cases, 

 and were attached just below the water-bottle. They were suspended 

 in a vertical position by a catch formiog part of the water-bottle ; this 

 was released by the first messenger, when the thermometers fall by 

 their own weight and reverse; they were hauled up in this reversed 

 position. This simple arrangement proved quite as satisfactory as any 

 of the more complicated reversing frames which are generally in use. 



CULTUEE MEDIA AND METHODS. 



The culture media employed for isolating and counting the bacteria 

 in plate cultures were the following : — 



I. Peptone Agar. 

 Peptone . . . . . . 2'0 grammes 



Potassium nitrate (KNO3) . . . 0*5 „ 

 Sea-Avater ..... 1000-0 c.c. 



Agar Agar . . . . . .18*0 grammes (of fibre) 



In the earlier work less Agar was used, but eventually it was found 

 more convenient to use a stifi'er jelly, and this did not appear to 

 hinder appreciably the growth of the bacteria. 



II. Potassium ]\Ialate Agar. 

 Potassium malate (C2H3(OH) < pqqt^) 1"0 gramme 



Sodium phosphate (NasHPO^ I2H2O) . 0-25 „ 

 Potassium nitrate (KNO3) . . . 0'5 „ 



Sea-water lOOO-Q c.c. 



Agar Agar ...... 12-0 grammes (of fibre) 



The medium was only filtered through glass wool, so that a very 

 slight fioccular precipitate of calcium phosphate was retained. 



