io8 



NATURE 



\yune 3, 1880 



erected in Greyfriars Church to an officer who died only in 

 1863 is no longer legible. At least f^th of an inch of sur- 

 face has here been removed from a portion of the slab in 

 sixteen years, or at the rate of about J inch in a century. 



In the second place, where a sandstone is marked by 

 distinct lamina of stratification, it is nearly certain to 

 split up along these lines under the action of the weather 

 if the surface of the bedding planes is directly exposed. 

 This is well known to builders, who are quite aware of 

 the importance of "laying a stone on its bed." Examples 

 may be observed in our churchyards, where sandstones 

 of this character have been used for pilasters and orna- 

 mental work, and where the stone set on its edge has 

 peeled off in successive layers. In flagstones, which are 

 merely thinly-bedded sandstones, this minuter lamination 

 is fatal to durability. These stones, from the large size 

 in which slabs of them can be obtained and from the ease 

 with which they can be worked, form a tempting material 

 for monumental inscriptions. The meLincholy result of 

 trusting to their permanence is strikingly shown by a 

 tombstone at the end of the South Burying Ground in 

 Greyfriars Churchyard. The date inscribed on it is 1841, 

 and the lettering that remains is as sharp as if cut only 

 recently. The stone weathers very little by surface dis- 

 integration. It is a laminated flagstone set on edge, and 

 large portions have scaled off, leaving a rough, raw sur- 

 face where the inscription once ran. In this instance 

 a thickness of about J inch has been removed in forty 

 years. 



. In the third place, where a sandstone contains concre- 

 tionary masses of different composition or texture from 

 the main portion of the stone, these are apt to weather at 

 a difterent rate. Sometimes they resist destruction better 

 than the surrounding sandstone, so as to be left as pro- 

 minent excrescences. More commonly they present less 

 resistance, and are therefore hollowed out into irregular 

 and often exceedingly fantastic shapes. Examples of 

 this kind of weathering abound in our neighbourhood. 

 Perhaps the most curious to which a date can be assigned 

 are to be found in the two sandstone pillars which until 

 recently flanked the tomb of Principal Carstares in Grey- 

 friars Churchyard. They were erected some time after 

 the year 1715. Each of them is formed of a single block 

 of stone about 8 feet long. Exposure to the air for about 

 150 years has allowed the original difterences of texture 

 or composition to make their influence apparent. Each 

 is hollowed out for almost its entire length on the exposed 

 side into a trough 4 to 6 inches deep and 6 to 8 inches 

 broad. As they lean against the w-all beneath the new 

 pillars which have supplanted them, they suggest some 

 rude form of canoe rather than portions of a sepulchral 

 monument. 



Where concretions are of a pyritous kind, their de- 

 composition gives rise to sulphuric acid, some of which 

 combines with the iron and gives rise to dark stains 

 upon the corroded suiface of the stone. Some of the 

 sandstones of this district, full of such impurities, ought 

 never to be employed for architectural purposes. Every 

 block of stone in which they occur should be unhesita- 

 tingly condemned. Want of attention to this obvious 

 rule has led to the unsightly disfigurement of public 

 buildings. 



III. Granites.— In Prof. Pfaff's experiments, to which 

 I have already referred, he employed plates of syenite 

 and granite, both rough and polished. He found that 

 they had all lost slightly in weight at the end of a year. 

 The annual rate of loss was estimated by him as equal to 

 00076 mm. from the unpolished and o'ooS5 from the 

 polished granite. That a poUshed surface of granite 

 should weather more rapidly than a rough one is perhaps 

 hardly what might have been expected. The same observer 

 remarks that though the polished surface of syenite was 

 still bright at the end of not more than three years, it 

 was less so than at first, and in particular that some 



figures indicating the date which he had written on it 

 with a diamond had become entirely effaced. Granite 

 has been employed for too short a time as a monumental 

 stone in our cemeteries to afford any ready means of 

 measuring even approximately its rate of weathering. 

 Traces of decay in some of its felspar crystals may be 

 detected, yet in no case that I have seen is the decay of 

 a polished granite surface sensibly apparent after expo- 

 sure for fifteen or twenty years. That the polish will 

 disappear, and the surface will gradually roughen as the in- 

 dividual component crystals are more or lesseasily attacked 

 by the weather, is of course sufficiently evident. Even 

 the most durable granite will probably be far surpassed 

 in permanence by the best of our siliceous sandstones. 

 But as yet the data do not exist for making any satisfac- 

 tory comparison between them. 



GERHARD JOHANNES MULDER 



T N the death of Prof. G. J. Mulder, to which we briefly 

 -'- alluded in our last number, Holland has been called 

 upon to mourn the loss of her leading chemist. Gerhard 

 Johannes Mulder was born at Utrecht, December 27, 

 1802. His studies were completed at the university of 

 his native city, and embraced especially mathematics, the 

 natural sciences, and medicine. In 1825 he established 

 himself as physician at Amsterdam. His inclination 

 towards a more purely scientific career caused him how- 

 ever in the year following to accept a position as teacher 

 of physics at Rotterdam under the auspices of the 

 Batavian Society. This proved but the stepping-stone 

 to the Professorship of Botany and Chemistry at the 

 Rotterdam Medical School, to which he was appointed in 

 1827. In 1841 he accepted a call to the Chair of Che- 

 mistry at Utrecht, and returned to the place of his birth, 

 to add to its fame by making it the scene of a long- 

 continued scries of valuable chemical researches. 



Mulder's tastes lay almost entirely in the department of 

 organic chemistry, and more especially in those branches 

 connected with the phenomena of vegetable and animal 

 life. In mineral chemistry his researches were confined 

 to careful studies on the chemical composition of white 

 lead and red lead (1839)— two of the important technical 

 products of Holland— and to the establishment of the 

 atomic weight of tin (1849) ^y means of numerous 

 analyses. He also modified or perfected a number of 

 analytical methods, such as those for the determination 

 of silver, phosphorus, carbonic acid, (Sic, and contributed 

 a large variety of analytical data on various technical and 

 scientific compounds. In 1S64 he made an elaborate 

 investigation on the phenomena of solution of salts in 

 water, establishing several of the now generally accepted 

 laws with regard to the solubility of mixtures of salts, 

 among others the interesting fact that in saturated solu- 

 tions of mixtures the relations between the respective 

 quantities of the salts is expressed in multipla of their 

 molecular weights. The varied experimental data result- 

 ing from his own researches were grouped, together with 

 the contributions of other chemists on this subject, in the 

 form of a monograph of over 300 pages, which forms the 

 most important work extant on solubility. 



In physiological chemistry Mulder has conducted a 

 large variety of investigations. The most important are 

 those connected with the study of the albuminoids, which 

 were commenced in 1838 and extended over a period of 

 twenty years. In the course of these investigations he 

 exposed albumin, fibrine, caseine, &c., to the action of a 

 variety of chemical agents, obtaining the products of 

 oxidation, chlorination, nitrification, &c. At an early 

 date he obtained, by the action of alkaline solutions on 

 the albuminoids, the so-called protein, which he regarded 

 as the primary albuminoid matter, the various members 

 of the group consisting of this radical in union with small 

 quantities of sulphur, phosphorus, and oxygen. This 



