Mr. Sorby on the Microscopical Structure oj Meteorites. 157 



The confirmation of these theoretical inferences by the St. Helena 

 observations appears to me to be quite as remarkable as that of my 

 primary hypothesis. If we arrange those observations in accordance 

 with the moon's position, and take the average daily height of the 

 barometer, we obtain the following 



Table of the Lunar Barometric Tides. 



Moon's 

 Position. 



Mean Daily Height of the Barometer at St. Helena, 

 28 inches + the numbers in the Table. 



1844. 



1845. 



1846. 



1844-6. 

 Average. 



o 







15 



30 



45 



60 



75 



90 



105 



120 



135 



150 



165 



180 



•2621 

 •2650 

 •2707 

 •2691 

 •2625 

 •2682 

 •2667 

 •2593 

 •2595 

 •2677 

 •2712 

 •2710 

 •2621* 



•3020 

 •3058 

 •3153 

 •3165 

 •3077 

 •3093 

 •3184 

 •3170 

 •3124 

 •3099 

 •3118 

 •3104 

 •3020 



•2701 

 •2693 

 •2707 

 •2688 

 •2688 

 •2783 

 •2800 

 •2721 

 •2686 

 •2691 

 •2715 

 •2735 

 •2701 



•2781 

 •2800 

 •2856 

 •2848 

 •2797 

 •2853 

 •2884 

 •2828 

 •2802 

 •2822 

 •2848 

 •2850 

 •2781 



This Table shows — 



1 . That the average of the three years corresponds precisely with 

 the theory, except in the secondary maximum, which is one day late. 



2. That the primary maximum occurred at the quadratures in 

 1845 and 1846, and one day earlier in 1844. 



3. That the primary minimum occurred at the syzygies in 1844 

 and 1845, and one day later in 1846. 



4. That 1846 was a disturbed year ; and if it were omitted from the 

 Table, each of the remaining years, as well as the average, would 

 exhibit an entire correspondence with theory, except in the primary 

 maximum of 1844. 



5. That 1845 was a normal year, the primary and secondary 

 maxima and minima all corresponding with theory, both in position 

 and relative value. 



" On the Microscopical Structure of Meteorites." By H. C. Sorby, 

 F.R.S., &c. 



For some time past I have endeavoured to apply to the study of 

 meteorites the principles I have made use of in the investigation of 

 terrestrial rocks, as described in my various papers, and especially 

 in that on the microscopical structure of crystals (Quart. Journ. 

 Geol. Soc. 1858, vol. xiv. p. 453). I therein showed that the pre- 

 sence in crystals of "fluid-, glass-, stone-, or gas-cavities" enables us 

 to determine in a very satisfactory manner under what conditions the 

 crystals were formed. There are also other methods of inquiry still 

 requiring much investigation, and a number of experiments must 



* Since the tabular numbers represent the semiaxes of the barometric curve, 

 and not the simple ordinates, the values for 0° and 1 80° are the same. 



