45, COENHILL, E.G., AND 122, REGENT STREET, W., LONDON. 



13 



FIG. 15. 



FIG. 16. 



FIG. 12. 



20. Negretti and Zambra's Students' Standard Barometer. In 

 laying off and dividing the scale of this instrument, allowances have been 

 made to compensate for the ordinary rise and fall of the mercury, making it 

 sufficiently accurate for observers who do not wish to incur the expense of 

 Fortin's arrangement for adjusting to a Zero Point. Fig. 16. Price 550 



