160 Dr. Waller's additional Observatio7is on Hail, 



pearance of hollow tubes, jointed at intervals, with a few 

 branches or subdivisions generally arising at the joints. The 

 particles which gave rise to this vegetation appeared to 

 me to belong to those which I have before described as the 

 irregular angular particles. Among these one or two infu- 

 soria were likewise seen, moving about with great rapidity. 

 When at rest their form was oval (A), but when in motion 

 their anterior extremity frequently became elongated, as at B. 

 Their organization was extremely simple; no filaments nor 

 appendages of any kind were to be detected about them. 

 Their interior had a granulated appearance. All these cha- 

 racters indicate that they belong to the genus Uvella of the 

 Monadinae, and probably of the species Uvella glaucoma 

 (Ehrenberg). C represents one perfectly circular, which 

 was in a state of constant motion, revolving round its centre. 



Atig. 3. — The vegetable filaments bad greatly augmented in 

 number. Small elongated cells, as represented, could be seen 

 at various places, as if forming the first elements of the tubulous 

 branches spread out around them. The infusoria had like- 

 wise greatly increased in number. 



Aug, 4. — The same appearances were presented as the day 

 before. Scarcely any alteration could be detected in the Ve- 

 getable and animal bodies: the last were as active in their 

 movements as before. I purposed to continue these observa- 

 tions every day, in order to ascertain their future changes; 

 but unfortunately by some accident one of the slips of glass 

 belonging to the apparatus was broken, and in consequence 

 the water quickly dried up, so that when next examined the 

 infusoria were found to be dead. The further addition of 

 water was ineffectual to restore the vegetable particles to life. 



For the purpose of repeating these observations, and likewise 

 for many others of a microscopic nature, the little apparatus 

 which 1 have made use of will be found very serviceable. It 

 consists of a small square piece of sheet caoutchouc, more or 

 less thick according as it may be required, with an aperture 

 cut in the centre about the size of a shilling. On each side 

 of it are placed two slips of glass of the same size, which, by 

 a moderate degree of pressure, may generally be made to 

 adhere to it so strongly as to render the little air-chamber, 

 where the india-rubber has been cut away, perfectly secure 

 from all access of dust and nearly air-tight. When the glass 

 does not easily adhere to the caoutchouc, this last may be 

 rendered sufficiently glutinous by heating it moderately. In- 

 stead of glass the plates may be of thin mica, which adheres 

 still better ; and from being so much more thin, will allow of 

 the employment of the highest magnifying powers without the 

 possibility of the access of foreign matter. I have sometimes 



