"The progress in the English department has been very great;--in barometers, thermometers, anemometers, and in every class of instruments. At the close of the Exhibition of 1851, there seemed to have arisen a general anxiety among the majority of makers to pay every attention to all the essentials necessary for philosophical instruments, not only in their old forms, but also with the view of obtaining other and better forms. This desire has never ceased; and no better idea can be given of the continued activity in these respects, than the number of patents taken out for improvements in meteorological instruments in the interval between the recent and preceding exhibitions, which amount to no less than forty-two." * * * "In addition to numerous improvements patented by Messrs. Negretti and Zambra, there is another of great importance, which they did not patent, viz. enamelling the tubes of thermometers, enabling the makers to use finer threads of mercury in the construction of all thermometers; for the contrast between the opaque mercury and the enamel back of the tubes is so great, that the finest bore or thread of mercury, which at one time could not be seen without the greatest difficulty, is now seen with facility; and throughout the British and Foreign departments, the makers have availed themselves of this invention, the tubes of all being made with enamelled backs. It is to be hoped that the recent exhibition will give a fresh stimulus to the desire of improvement, and that the same rate of progress will be continued." To fulfil the desire of the International Jury in the latter portion of the above extract will be the constant study of NEGRETTI & ZAMBRA. _1st January, 1864._ TABLE OF CONTENTS. CHAPTER I. INSTRUMENTS FOR ASCERTAINING THE ATMOSPHERIC PRESSURE. SECTION 1. Principle of the Barometer. 2. Construction of Barometers. 3. Fortin's Barometer Cistern. 4. STANDARD BAROMETER. 5. Correction due to Capillarity. 6. " " Temperature. 7. " " Height. 8. The Barometer Vernier. 9. SELF-COMPENSATING STANDARD BAROMETER. 10. BAROMETER WITH ELECTRICAL ADJUSTMENT. 11. PEDIMENT BAROMETERS. 12. The Words on the Scale. 13. Correction due to Capacity of Cistern. 14. PUBLIC BAROMETERS. 15. FISHERY OR SEA-COAST BAROMETERS. 16. Admiral FitzRoy's Words for the Scale. 17. Instructions for Sea-coast Barometer. 18. French Sea-coast Barometer. 19. COMMON MARINE BAROMETER. 20. THE KEW MARINE BAROMETER. 21. Method of verifying Barometers. 22. FITZROY'S MARINE BAROMETER. 23. Words for its Scale. 24. Trials of this Barometer under Gun-fire. 25. NEGRETTI AND ZAMBRA'S FARMER'S BAROMETER AND DOMESTIC WEATHER-GLASS. 26. Rules for Foretelling the Weather. 27. Causes which may bring about a Fall or a Rise in the Barometer. 28. Use of the Barometer in the Management of Mines. 29. Use of the Barometer in estimating the Height of Tides.